I would expect a large provider like Hetzner to refresh hardware continuously - every year a fraction of old hardware is retired and replaced by new. Given price shock they could stop doing this but older hardware is less energy efficient and has limited life anyway.

Hetzner mostly ate up the rising energy prices in germany for the last 3 years and they have big problems with their hardware supply since then. It is hard to get cloud instances in nbg and fsn. So an increase in pricing is very much expected from my side.

In their email they say their operating costs increased too. Whether it actually did or not, that is their reasoning to increase prices on already sold products.

Power and cooling costs also play a role, probably.

Even if you have an unbelievable PUE of 1.00, you are still affected by the energy cost increases. There's no running from that.

Edit: I misremembered the PUE formula. This comment has been edited to correct my mistake.

Even existing hardware can fail, and swapping out memory or disks is expensive these days. :-(

Variable costs increase ? (Floor space rental, Energy, Salaries, licenses, other services ...)