Proof of stake just doesn't work the same as mining from an economic incentive standpoint.
Miners make real-world investments, in advance, in equipment that becomes less valuable as difficulty increases.
Miners have no guarantee that their investment will pay off, they merely have a probability of finding a good proof of work.
Staking chains are vulnerable ...
Is this the correct way to calculate security for bitcoin proof of work?
Not sure. But looks like lot of things are ignored in these numbers. I have read about FRM so I will share few things related to FRM ratio and security:
The Fee Ratio Multiple (FRM) is defined as the ratio between the total miner revenue (blocks rewards + transaction fees) and ...