I stumbled on this sheet while browsing another forum:
https://docs.google.com/spreadsheets/d/11hd-Q6KdkNETiRBs_JYwxOEAEfiEM4YoYad__grb5lE/edit?usp=sharing

Basically, this is an attempt to calculate the cost of mining 1 btc for Marathon and Riot (the infamous big players).

The numbers were surprising to me, and I've noticed some errors, like the hashrate was not 225 EH on average in Q1, and a little more bitcoins were produced than 900*90 since, I guess, when hashrate is constantly growing we have more blocks generated than expected 2016 per 2 weeks. This lowers final numbers by 10-15% but still way too high IMO. The SEC filings are useful, but I'm not familiar enough with the terms to be able to verify them.

Anyway, thought it would be useful to share it here.