They are getting paid, consider how many people donate.
The difference is that there are thousands of tweaks out there that cost a dollar or two, and not every single user that jailbreaks their phone buys those tweaks, however every single user would be paying a jailbreaker for the jailbreak, $30 is absolutely crazy!
The jailbreak for iPhone 4S and iPad 2 got downloaded a million times on the very first day, if it cost $30, that means the jailbreaker would be earning $30 million in one day. Are you serious?
Besides that, consider how many serious companies would get involved into this when they could be making so much money, soon all of this would get out of hand, Apple would get involved and it would either be banned or they'd really close all the loop holes... don't you think Apple knows what they are doing? Jailbreaking and freedom to modify your device and yes piracy, sells hardware.
If you want to pay them so much, go ahead and donate.