[tveita]

Only by as much as the miners themselves spend. And it's a running cost, you have to spend it every day, while an attacker would spend it only during their attack.

The only way to make a 51% attack impractically expensive is to make the network impractically expensive to run.

[CyberDildonics]

That would only make sense if you could somehow rent 51% of the hashrate, which isn't remotely true.

[gritzko]

Another option is to hack 51% of the hashrate. The third one is to own it from the very beginning.