Ballpark math says you could sustain it for half an hour on Hetzner for $5k-$6k (only from 1500 IPs though), at least if your account didn't get banned first and you're halfway decent at network programming. I have no idea what a proper botnet like this costs though or how large the profit margins are.
Yeah I assume there's the initial startup cost of successfully managing to infect a large network of devices, and then the cost for any given use is likely "what customers will pay for it". If they are selecting out big money targets and focusing on gaming, I'm guessing the price isn't that high, but they also presumably know interesting a state actor in taking them down either by changing targets or bringing in enough money is bad for business.
The idea is, the botnets are in control of someone else. Who "owns" them. And some of those will rent "their property" for money, like they would legitimately own them.
Depends. The more the owners use their bots, or let others use their botnets, the more attention there is to them and the less useful the botnet is (either blacklisted IPs or owners noticing).
And a little bit of malicious bandwidth is easy to hide, a lot not. So there is a price to bandwith to the criminal owner.
