Every few months a marketer asks the same question: why pay per text when Instagram DMs are free, WhatsApp has two billion users, and Viber is big in half of Europe? The question is fair. The answer depends less on price and more on three things: who is allowed to send the first message, what happens to your account when you get it wrong, and whether your audience actually opens that app.
We make Ready, an SMS and iMessage platform, so we have a side in this. We'll also say where social messaging beats SMS, because in several markets it does. This post compares the four channels on reach, rules and risk, then works through the cost of a real send.
The short version
- Instagram DMs are a reply channel. The official API lets a business answer people who messaged first, inside a time window. Mass cold DMs from a personal or business account are what gets accounts restricted.
- WhatsApp Business Platform allows business-initiated messages, but only through pre-approved templates, to users who opted in, with per-message fees Meta sets by category and country.
- Viber Business Messages run through authorized partners and work well where Viber is the default messenger. In the US, few people use it.
- SMS reaches nearly every US mobile number with no app required. In exchange you register (A2P 10DLC), honor STOP, respect quiet hours, and text only people who consented.
Reach: does your audience open the app?
This matters more than anything else on the list. A cheaper channel your customers never check doesn't save you money.
| Instagram DM | Viber | SMS | ||
|---|---|---|---|---|
| Needs an app installed | Yes, plus an account | Yes | Yes | No, every phone |
| Strongest markets | Global, younger audiences | Latin America, India, much of Europe, Middle East | Eastern Europe, Philippines, parts of the Middle East | US and Canada |
| Who can start the chat | The user, effectively | The business, with an approved template and opt-in | The business, via a partner and approved sender | The business, to consented contacts |
| Identifier you need | Instagram handle that messaged you | Phone number with WhatsApp | Phone number with Viber | Phone number |
| Cost model | No per-message fee via API | Per message, priced by Meta | Per message, via partner | Per segment |
If your list is mostly US consumers, SMS and iMessage are the default inboxes. WhatsApp use in the US is real but uneven, and it clusters in certain communities and in people with family abroad. If you sell into Brazil, Spain or India, the picture flips, and WhatsApp should probably be your primary channel. We go deeper on that split in bulk SMS vs WhatsApp for US business messaging.
Rules: who gets to send first
Instagram's messaging API is built for conversations the user starts: a DM, a story reply, a comment that triggers an automated reply. The business can respond within a standard window after the user's last message. Outside that window, options are narrow. Third-party "mass DM" tools that log into your account and fire messages at follower lists break Instagram's terms. They work until the account gets action-blocked or disabled.
Instagram is excellent for converting people who are already engaging with your content. It is not a way to send a sale announcement to 5,000 customers.
WhatsApp is closer to SMS than most people expect. Business-initiated messages have to use templates Meta approves ahead of time. Templates are categorized as marketing, utility or authentication, and each category is priced differently. You need opt-in. Each number also carries a quality rating and a messaging limit: a new number can reach a limited count of unique users per day, and the cap rises as your quality holds up. Too many blocks and reports lower the rating and can pause sending.
Viber
Viber Business Messages go through authorized partners who register your sender identity. Promotional sends need consent, and the mechanics depend on the partner. Where Viber dominates, it can carry rich content such as images and buttons in a branded thread. Where it doesn't, your message reaches only the small share of your list that has the app.
SMS
US business texting runs on registered routes. You register a brand and a campaign (A2P 10DLC), and carriers filter unregistered traffic. Our 10DLC explainer covers this in detail. Beyond registration:
- Text only people who opted in. On Ready, cold contact belongs on phone and mail, and SMS goes to consented or replied leads.
- Honor STOP. On Ready, an inbound STOP propagates so that contact can't be texted again from any campaign.
- Respect quiet hours. Ready holds sends outside permitted local hours based on the recipient's area. Campaigns, drip campaigns and automations wait up to 24 hours for the window; a one-to-one or API text is held only if the window opens within 6 hours, otherwise it is refused and must be resent; a one-to-one reply to someone who texted you in the last 24 hours goes out at any hour.
- Keep consent records. Ready logs your opt-in attestation for each campaign you send and each API send that attests consent (who sent, to how many, when). Recipient-level proof, such as opt-in time, wording and page URL, has to live in your own store.
If you're also weighing toll-free or RCS as sender types, see 10DLC vs toll-free vs long code vs RCS.
Risk: what a mistake costs on each channel
The penalty for getting it wrong works differently on each channel:
- Instagram: the platform restricts or bans the account. For a brand whose audience lives on that handle, losing it can cost more than any fine.
- WhatsApp: your quality rating drops, your messaging limits shrink, or the number gets restricted. Meta enforces this, and appeals are slow.
- Viber: the partner and Viber enforce sender rules, and you can lose the sender ID.
- SMS: carriers filter messages or suspend the campaign. Legal exposure also sits on top. The TCPA allows roughly $500 to $1,500 per text for unconsented messages, which is why compliance is more than a box-ticking exercise.
Ready's compliance tools reduce that exposure without removing it. The TCPA and DNC litigator scrub screens numbers against known litigator and DNC-complainer lists. The standalone scrub costs $0.005 per contact. Switched on for an account, scrubbing is $0.003 extra per segment, and it is off by default. Compliance is still the sender's responsibility. No tool makes you lawsuit-proof.
Cost: a worked example
Assume a retailer wants to send a restock notice to 2,000 opted-in US customers. The message is 140 characters of plain text with no emoji, so it fits in one GSM-7 segment (the limit is 160).
On Ready Standard:
- Ready rate: 2,000 × 1 segment × $0.0075 = $15
- Carrier fee: 2,000 × $0.0045
- Total: $40 plus 2,000 × $0.0045. That excludes the optional compliance surcharge.
Add one emoji and the same 140 characters becomes 3 segments, because the per-segment limit drops to 70 characters and multipart messages carry 67 each. That roughly triples the bill: 2,000 × 3 × ($0.0075 + $0.0045). Check the segment count before you add the emoji.
Ready's all-in prices per segment include the carrier fee but not screening: Scrub lists and Number validation, the two switches in Settings under Compliance, each add $0.003 per segment when switched on, shown as screening on your bill, and both are off by default. Unless you turn the opt-out footer off, the first text to each contact, and one again from time to time, also gets "Reply STOP to opt out" and your business name if the message does not already have them, so a text close to the segment limit can bill one more segment.
Registration has no setup fee. The first month, $25, is charged at submit. After that the monthly fee is $25/mo for registration and $2 per number. Most approvals take 2 to 7 days.
Ready isn't the lowest per-segment option. Raw carrier APIs like Twilio, and GoHighLevel's LeadConnector, cost less per message. What you get with Ready is in-app registration, opt-out handling, quiet hours, scrubbing, a two-way inbox and campaigns in one place. Our Twilio alternatives cost comparison has the full breakdown.
An Instagram reply is free per message, but you can't use it to broadcast. WhatsApp marketing templates are priced per message by Meta, and the price varies by country. Check Meta's current rate card for your market and run the same multiplication. In some countries WhatsApp works out cheaper than SMS, and in others it doesn't.
Where iMessage fits
Some teams want the rich, branded feel of WhatsApp while staying on the inbox US iPhone users already open. Ready's blue line sends as iMessage, so messages show up blue with your business name and photo. It doesn't need 10DLC registration.
The blue line costs $99 a month per line plus 6 cents a segment, and replies are also 6 cents a segment. Each line can start up to 50 new conversations a day, and Android recipients get texts from your regular number at the regular price if you already had a number; if the blue line came with its green number, your account's texts bill at 6 cents a segment once you register. Campaigns send from regular numbers, not the blue line, so think of it as a conversation channel rather than a broadcast channel. iMessage for business vs Apple Messages for Business explains how it differs from Apple's service.
How to choose
- US audience, time-sensitive broadcasts: SMS. It needs no app, and you can register in days.
- International audience in a WhatsApp market: WhatsApp Business Platform with approved templates.
- Audience concentrated where Viber is the default: Viber through a partner.
- Followers already messaging you: Instagram automation for replies. Don't build a broadcast plan on it.
- Mixed audience: run more than one channel. A common setup is SMS for US customers and WhatsApp for international ones, with each customer's channel recorded at opt-in. SMS vs Messenger and WhatsApp for Business covers the operational side.
The takeaway
Social bulk messaging isn't free SMS. Instagram mostly won't let you initiate. WhatsApp and Viber let you initiate under template, opt-in and quality rules, and they charge per message. SMS reaches everyone with a phone number, but only after registration and consent. Choose by where your audience actually reads, then budget with segment math.
If SMS fits, you can start on Ready at /signup. The first 20 one-to-one texts are free, so use them before you register. To send, you add a card and get a number, which is $2 a month with the first month charged when you get it. Developers can go straight to the bulk messages API docs.