You're being billed for heads.
You bill for clients.
That mismatch is the whole problem. Per-seat pricing grows with your headcount; your revenue grows with the number of clients you serve. Paste your current quote and see the difference.
$0.33/user on ContentNest
How this is worked out. ContentNest's flat plans are priced on the number of client organizations you run a portal for, with storage and bandwidth included and a low per-GB rate beyond your plan's limits. Your learner count does not move the price. The figure above is the cheapest published plan that fits the shape you entered — it is an estimate from list prices, not a quote.
If what you actually want is a predictable number. That is usually the real reason a per-seat quote looks appealing — not the per-seat part, the budgetable part. Commit annually and you get one fixed figure for the year. Past a certain size the right answer is a contract rather than a list price, and per-active-user seats are available there too. Seats stay on the table; they are just not the default, and they are not the only way to get a number you can plan against.