10s of the thousands in the same month would indeed move you into our paid plan. If this was more like <10k per month for many months, you'd still be able to do that on our free plan.
I meant that if you were running something like Discord where you have users who over a year make $100s worth of notifications then that use case doesn't match the pricing model compared to a use case where you are dealing with a few users (where one @ doesn't refer to thousands of people)
Ooooh yeah, got it. We have lower per-message prices for customers sending at scale. We have our own hard costs to account for, but we work hard to make sure Courier can fit into most teams' budgets.