It’s cheaper to run 1 more GPU when you are already running 100
It’s the same price to add 1 eth when you own 100 eth as when you own 1 eth
Kind of, but doesn't that assume a linear utility function for holding eth which I think seems unrealistic? Plus, there are costs associated with holding eth (cold storage etc) which seem fixed, so its cheaper to securely stake 1 additional eth when you're already staking 100eth than when you're not running any. Plus fixed costs of actually running a staking business (by analogy with a mining business).
If I have 100 GPUs and I buy one more can't I turn around and say "But buying one more GPU is just buying one more GPU"? Even if your point is that electricity bills are lower per additional GPU, surely humans discount the value of incremental money after some point so for those with lots of eth incremental eth isn't worth as much?