Every provider in this category charges for the phone line, not the message. Sendblue lists $100 a month per dedicated line. Miss Blue lists $198 for a dedicated number and $78 for a shared one. Nobody meters per send.
That is not a pricing strategy somebody chose. It is a description of the underlying architecture leaking into the invoice.
Why the line is the unit
Because Apple sells no API, these providers run the Apple side themselves — real accounts and devices, operated at scale. The full explanation is here, but the commercial consequence is what matters: the scarce, expensive resource is the *number*, and once a number exists, the marginal message costs approximately nothing.
So the bill tracks the numbers. Everything else follows:
- A dedicated number costs more than a shared one, because it is dedicated hardware and identity rather than a pooled one.
- There is no free unlimited tier, because there is physical infrastructure behind every line.
- Sandboxes are free but capped — Sendblue's allows up to 10 verified contacts, Miss Blue's has no live number at all.
- Enterprise pricing is about line count, not message volume.
Who this model favours
Small senders, unusually. On metered SMS the small business is the worst-value customer: all the fixed overhead of registration and number rental, none of the volume to amortize it. Per-line pricing inverts that.
| Messages per month | Cost per message |
|---|---|
| 200 | $0.495 |
| 800 | $0.124 |
| 2,000 | $0.050 |
| 5,000 | $0.020 |
Two hundred messages a month is expensive per message and irrelevant in absolute terms — $99 is less than most businesses spend on a single ad. The number that matters is not cost per message, it is whether the whole line pays for itself.
The break-even calculation
One line of arithmetic decides this, and it is not about messaging at all:
How many additional outcomes per month does this need to produce to cover the line?
| Business | One outcome is worth | Break-even at $99/mo |
|---|---|---|
| Dental practice | $180 cleaning slot | Under 1 prevented no-show |
| HVAC contractor | $450 service call | Under 1 recovered job |
| Salon | $85 appointment | About 1.2 filled cancellations |
| Restaurant | $140 four-top | Under 1 recovered booking |
| Ecommerce, $60 AOV | $60 order | About 2 recovered carts |
For most service businesses the answer is *one*. That is a low enough bar that the interesting question is not whether it breaks even but whether you will measure it well enough to know — which is a different problem, and the one people actually get wrong. Tag the links before the first send.
The freedom nobody uses
The most valuable consequence of per-line pricing is behavioural. When the marginal message is free, you can afford to send the message that is merely *useful* rather than only the ones that are strictly necessary — the arrival notice, the 'your car's ready', the photo of the finished job. That is where the goodwill in this channel comes from, and metered pricing quietly prevents it.
The caps to read before you sign
- Inbound contact limits. Sendblue's per-line tier lists 1,000 inbound contacts daily. Generous for a small business; worth knowing if you are running a broad campaign.
- Shared versus dedicated. A shared number is cheaper and fine for testing. For production, a number that is yours is worth the difference.
- Fair use on 'unlimited'. Miss Blue describes its dedicated tier as unlimited on messages, contacts and seats. Ask what the fair-use position actually is before you plan around it.
- Promotional rates. Miss Blue's discounted pricing is described as locked in for accounts created during the sale. Confirm the terms rather than assuming.
Current tier detail for all five providers, with the caveat that this category changes fast, is on the provider comparison page. For the two most-compared options specifically, Sendblue vs Miss Blue works through which one you actually are.