Isn't the idea behind botnets that no one is paying for the bandwidth, besides the unsuspecting random people who have fallen victim to malware?

I'd imagine the pricing is quite disconnected from the price of "legitimate" bandwidth. But I don't know in what direction.

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.