I don't think they they'll need to increase, fly.io is already rather expensive as far as cloud offerings go today: shared 8 vCPU / 16GB VPS is $85/mo at fly, Hetzner is $16/mo for the same.
Whatever the answer is, it’s probably the same answer for why many companies would likely be willing to pay more for fly.io than Hetzner as well.
Through also it's not a fair compression because for the kind of services where being close to the edge and redundant over many places matters Hetzner isn't even an option. AWS maybe, but AWS is also pain in my experience.