Your idea is based on the concept that people who are perma-banned will simply make a new account anyway, so why not have them pay to have the account reinstated. They'd get the account back and staff would sink some TC along the way. Win win.
But actually, this really doesn't do anything good for the community.
All this is going to do is give people who screw up enough to get perma'd, leeway. And if someone has screwed up enough to get permanently banned, they really shouldn't have it.
You are correct in saying that most people who are banned/perma banned make another account. But in most cases, people who are banned want their main account unbanned. And I've seen people who've been banned for years on alternate accounts come back to Ban Appeals to get their main back.
As to why they do this, I'm sure it's various reasons. Whether it be the name, items, qi ect.
Encouraging the mindset of "I've got TC to spare, might as well do something stupid to get myself perma'd. I can just pay to get out anyway!" isn't something staff want to do, I'm almost certain.
To be honest, it just sounds like you liked the idea of having a bail system in Toribash, rather than it actually being an improvement to the system.
The cons far outweigh the pros in this scenario. Main pro being TC being sunk, which honestly doesn't matter at all. There are plenty of ways to do this.