Yea but the cost is not a fixed monthly sum and things can go wrong as we can see from the blog post.
An accident could bankrupt the dev.
A dedicated server will always cost the same so you always know how much you pay.
It will cost 40 Euro/month to have 6 cores/12 threads,64gb of ram and 1Tb of ssd.
Dirt cheap compared to any other alternative
They say they're receiving $500/mo in donos and that it's currently just enough to cover their infra costs. Given 300 million 70 KB files, R2 + high cache hit ratio would work out to about $300 in storage-months + request costs, or $600/mo with Cache Reserve and then they'd always hit cache if I understand the project right: meaning the costs shouldn't blow up beyond that, and that request count would essentially just not matter.