Per-seat or flat rate: where the lines cross

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Most business software charges per seat: a price for each person who uses it, every month. A smaller group charges a flat rate: one price, however many people you add. The difference looks trivial when there are four of you. It stops being trivial faster than most people expect.

The two shapes, with real numbers

Checked on 24 September 2026:

Slack is per seat. The Pro plan is listed at $8.75 per user per month billed monthly, or $7.25 per user per month billed annually. Business+ is $18 monthly, $15 annually.

Basecamp is flat. Its Studio plan is listed at $59 a month with unlimited users, and its own page states you can "add as many people as you want at no additional cost."

Those two products do different jobs, and this is not a suggestion to swap one for the other. What matters here is the shape of the price, because that shape is what your future hiring runs into.

Where the lines cross

At $7.25 per seat, $59 buys you a little over eight seats. So a flat $59 plan costs less than an eight-seat per-user plan from the ninth person onwards — and from then on the gap widens with every hire, because one line keeps climbing and the other does not.

That crossover point is the number worth knowing before you commit, not after. It moves with the per-seat price, so work it out for the tools you are actually considering:

What this changes about how you buy

Count the seats you will have, not the seats you have. If you expect to double this year, a per-seat tool roughly doubles with you. A flat plan does not.

Watch for the seats you are not using. Per-seat billing usually charges for anyone with an account, whether or not they log in. Contractors, people who left, a spare admin login — all billable. This is the single most common way small teams overpay, and it is invisible unless you go looking.

Check what the flat plan caps. Flat-rate plans rarely have no limits at all. They cap something else instead — projects, storage, features. Basecamp's own tiers differ by project count and storage rather than by headcount. A flat price that caps the thing you need most is not cheaper, it is just differently expensive.

Do not assume flat is better. For three people, per-seat is usually far cheaper. The point is not that one model wins; it is that the model decides how your bill behaves as you grow, and that is worth five minutes before you sign.