Sounds like a completely legitimate use though. Hetzner were widely telling people about that 20TB limit, so why would they be surprised when people use them as CDN boxes?
Where's the surprise? It's the classic business 2-step - drum up interest with "too good to be true" features, then cut them back. The marginal customers who need those features leave (and are too expensive to keep), everyone else is used to your product and stays.
That or they just didn't dimension well their prices and now it's biting them back.
I prefer to assume naivety over malice/negligence.
Until you remember that marketing is a separate department from finance which is a separate department from ops/engineering.
The engineers said 20TB in aggregate was fine but likely didn’t consider the “bad apples”. Marketing obviously wants to use the biggest numbers and then finance comes in with the hammer and dev points to egress as an simple way to upset rhe fewest number of real customers.
It does make sense: The average was low enough that a 20TB cap worked. Then marketing started boasting about the 20TB limit and attracted a bunch of high-bandwith customers, thereby driving up the average making 20TB decidedly "not fine".
As an engineer, if you don't qualify whether your answer is average or max, you've messed up.
I'm confident the marketing folks would just say something akin to "shut up nerd", cash their bonuses, and leave you with the problem.
As an engineer, NEVER give out averages without checking that they are consistent with the distribution of the actual data.