Email is basically free to send. SMS is not. That single fact should shape how you plan a peak-season blast, and yet most DTC operators walk into Black Friday having budgeted the ad spend down to the dollar while treating the text campaign as a checkbox in their ESP. Then the invoice shows up and the "cheap" channel cost more than the paid social they agonized over.
Full disclosure: I work for Ready, so I sell SMS for a living. That's exactly why I want you to run the segment math before you hit send — because a blast that's under-budgeted gets throttled, cut short, or worse, sent without anyone realizing it doubled in cost when someone added an emoji to the copy.
Let's build the real total cost of a Black Friday SMS campaign to 80,000 contacts, then put it next to email's near-zero marginal cost, and figure out where SMS still earns its keep.
First, count segments — not messages
The number that matters isn't "80,000 contacts." It's segments. One SMS segment is 160 GSM-7 characters. Go one character over and the whole message splits into multipart pieces of 153 characters each. Drop a single emoji or a curly quote and you've switched to unicode encoding, which cuts the limit to 70 characters (67 per part when multipart).
So the exact same 175-character promo can bill as either 2 segments (plain text) or 3 segments (with one emoji). That's a 50% cost swing from a single 🎁.
Here's what typical Black Friday copy looks like in segments:
| Message | Chars | Encoding | Segments |
|---|---|---|---|
| "BLACK FRIDAY: 30% off everything. Code BF30. Shop now: rdy.co/x" | 62 | GSM-7 | 1 |
| Above + "Ends midnight. Reply STOP to opt out." | 99 | GSM-7 | 1 |
| Full promo with details + one emoji | 175 | unicode | 3 |
| MMS with a hero product image | — | MMS | billed as MMS |
The lesson before you spend a dollar: write your copy, paste it into a segment counter, and know whether you're sending 1, 2, or 3 segments to every contact. It's the biggest lever you have.
The worked TCO for 80,000 contacts
Let's price three realistic versions of the same campaign on Ready's Standard tier ($0.02/segment + $0.0045 carrier pass-through = $0.0245 all-in).
Scenario A — tight 1-segment copy (no emoji): 80,000 × 1 × $0.0245 = $1,960
Scenario B — the emoji promo, 3 segments: 80,000 × 3 × $0.0245 = $5,880
Same audience. Same offer. A $3,920 difference because someone thought the message needed a fire emoji and a second sentence.
Now here's where volume changes things. Ready's Growth tier drops the per-segment rate to $0.016 (all-in $0.0205) automatically once you pass 50,000 segments in a calendar month. You don't apply for it or pick a plan — it just kicks in.
In Scenario A, 80,000 segments crosses 50,000 mid-blast. The first 50,000 bill at $0.0245, the remaining 30,000 at $0.0205:
- 50,000 × $0.0245 = $1,225
- 30,000 × $0.0205 = $615
- Total: $1,840
In Scenario B (240,000 segments), the crossover happens almost immediately:
- 50,000 × $0.0245 = $1,225
- 190,000 × $0.0205 = $3,895
- Total: $5,120
If you already send transactional and abandoned-cart texts all month, you may hit the 50k threshold before Black Friday even starts, meaning your whole blast prices at the Growth rate. Worth checking your month-to-date volume the week before. There's more on the crossover mechanics in the volume-tier margin breakdown if you want to see it from the reseller side.
The MMS crossover
An MMS — image, GIF, richer layout — bills as a single MMS unit rather than splitting into segments. For a long, image-heavy Black Friday message that would otherwise be 3+ unicode segments, MMS can actually be comparable or even competitive per contact, because you're not multiplying by segment count.
But there are two catches worth naming:
- MMS costs more per unit than a single SMS segment. It only pencils out against multipart SMS, not against a tight 1-segment text.
- Carriers silently compress or strip images. Your crisp product hero can arrive as a blurry thumbnail because of the ~600KB ceiling most carriers enforce. I wrote about that failure mode in the MMS image-compression post — read it before you commit your whole campaign to an image.
Rule of thumb: if your copy naturally fits in one clean SMS segment, send SMS. If it's going to sprawl into 3 unicode segments and an image genuinely lifts conversion, model the MMS number and compare. Don't default to MMS because it looks nicer in the composer.
Email's near-zero marginal cost
Here's the honest comparison. Sending that same 80,000-contact blast by email costs you approximately nothing on the margin. Most ESPs bill on list size or a monthly plan, so the 80,001st send is free. There's no per-message carrier fee, no segment multiplication, no emoji penalty.
So on raw send cost, email wins by a mile — it's not close. If you only look at the cost column, you'd never send SMS at all.
Which is exactly why the cost column is the wrong place to make the decision.
Where SMS still wins — on the revenue side
SMS open and read rates run far higher than email — opted-in lists commonly see read rates in the 90%+ range and click behavior that dwarfs a promotional email that lands in the Promotions tab (rough industry approximations, not guarantees). A subscriber who explicitly gave you their number and consent is a fundamentally more valuable contact; we've argued elsewhere that an SMS subscriber is worth 3–5x an email subscriber when you actually treat the channel differently.
So the real question isn't "which is cheaper" — it's "does the incremental revenue clear the incremental cost." Let's put numbers on Scenario A at the Growth-blended cost of $1,840 for 80,000 contacts:
- Break-even at a $50 AOV means you need ~37 incremental orders across 80,000 texts to cover the send. That's a 0.046% conversion rate.
- Any realistic Black Friday SMS conversion — even a conservative fraction of a percent — clears that bar many times over.
The cost is real, but it's small relative to the revenue an engaged list produces on peak day. The danger isn't that SMS is expensive; it's that it's invisible until the invoice, and that people over-send. If you want to check where extra sends stop paying for themselves, the revenue-per-send peak analysis is the companion piece to this one.
Don't blow the budget on contacts you shouldn't text
Two line items quietly inflate a peak-season TCO:
- Dead weight. Texting 80,000 contacts when 15,000 haven't engaged in six months means you're paying full segment cost to subsidize non-buyers. Segment your list; the math on where that ceiling sits is in the win-back cost-ceiling post.
- Compliance exposure. TCPA damages run $500–$1,500 per text. One bad blast to numbers without valid consent, or a send that ignores quiet hours, dwarfs your entire campaign budget. Ready enforces quiet hours by recipient area, honors STOP automatically across campaigns, and offers a standalone litigator/DNC scrub at $0.005/contact — a 80,000-contact scrub is $400, cheap insurance against a single six-figure claim. It's not lawsuit-proofing; consent is always your responsibility. But it's the correct order of operations.
The pre-send checklist
Before you schedule the Black Friday blast:
- Paste your copy into a segment counter. Know your segment count per message and whether an emoji tipped you into unicode.
- Multiply honestly: contacts × segments × all-in rate. Model both Standard and the Growth crossover if you'll pass 50k this month.
- Decide SMS vs MMS on the actual numbers, not on how it looks in the composer.
- Trim the list to contacts with valid consent and recent engagement.
- Scrub for litigators/DNC if any part of your list is older or imported.
- Confirm quiet-hours handling so your midnight-deadline copy doesn't send at 11pm local to the wrong coast.
The takeaway
Email's marginal cost is basically zero and SMS's isn't — that's true and you shouldn't pretend otherwise. But an 80,000-contact SMS blast that costs $1,840 to $5,880 depending on your copy is trivially profitable against an engaged, consented list on the highest-intent shopping day of the year. The failure mode isn't the price. It's sending blind: not counting segments, not noticing the emoji penalty, not knowing the Growth tier kicked in, and over-texting people who'll never buy.
Run the segment math first. If you want to see the per-segment breakdown against your own volume, the Ready pricing and product page has the tiers and pass-through laid out, and you can start with 2,500 free credits to test your copy's real segment count before you commit the whole list.