I wouldn't be surprised if the Bitcoin network already costs more than those mainframes in terms of carbon footprint - after all, the Bitcoin network is basical

I wouldn't be surprised if the Bitcoin network already costs more than those mainframes in terms of carbon footprint - after all, the Bitcoin network is basically the world's largest supercomputer [0]. On top of that, you have to consider that those systems offer much more value than just a barebones ledger as the core of Bitcoin does. If you add in all those companies building stuff on top of Bitcoin, the comparison starts to become less favorable. [0] Purely monetary terms are obviously different. The vendors of those systems inflate prices ridiculously because they can - banks have traditionally not been under much pressure to operate efficiently in this arena.