Infect 100 servers with miner and get 10$ monthly for each, its 1000$ per month.
Have in mind that those kind operations can be huge and infections are done using automated scripts to search and install virus miners on 1000 of servers, i doubt its done manually one by one server.
I have server two Xeon 12 core 24 thread mining ETN in January, I get 30 ETN per day. I believe there have are many servers infected and someone or admin don't know.
the comment manji is true :
(but that fact don't influence hacker because he/she nothing to lose because a server, mobile phone not his)
yes, they (hacker) nothing to lose because their don't buy hardware, paying electricity, paying internet. they just sit and look at the balance in the wallet.