Progressive is something like income tax. If you earn more than $X, you will pay more than base rate on what's more than $X. Like US tax brackets - 10%, 15%, 25%, 28%, 33%, 35%, and 39.6%.

Atlassian pricing is the inverse of that, if the US does that, it will be like 39.6% for income up to $9000, then 35% up to $37000 etc.