Why don't you run a miner on your computer and find out.

If you're paying for your energy and equipment it'll most likely be a negative in terms of profit but would be a fun experiment and espouse a hacker ethos.

Plenty of perfectly fine working rackmount servers are replaced every year because for their power/space footprint you can put something that's about to do 50% more work.

Otherwise an accountant would tell you it is something like the cost of ownership: Let say very roughly $0.5 per cpu/per day.