How does something like CCBill stay in business when the card networks themselves have strict guidelines on chargeback rates that'll get you booted from the network?

Presumably, such merchants are basically outsourcing their chargeback resolutions to CCBill, who I assume is quite good at fighting them via proof of purchase.

They charge 10% (or at least they did ~10 years ago, probably higher now) and require you maintain a 30% reserve and then they use that money to continue to lobby Visa/MC to prevent competition.