They take donations.

Just to nitpick, that doesn't imply profit. They could be breaking even (and probably are working at a loss).

I don’t think any of them are breaking even when you consider the maintenance costs, I just thought it was kind of funny considering the nature of the line of work they are in.

This was a different group of people but when some of the old LibGen domains got seized the FBI uploaded photos of the owners and the things they had spent their money on; a crappy old boat, what looked like a trailer in rural Siberia, and a vacation somewhere in the Mediterranean. It honestly read like sketch comedy, because the purchases didn’t appear remotely ostentatious.

Z-library also supposedly caps downloads at 5 per day and offers more and faster downloads to paying subscribers.