California small claims court costs like $50. If you win there's a permanent ruling against the landlord.

It's worth going through the process just to learn. It's also crazy how difficult it is.

Do you mean that it’s noticeably more difficult than the equivalent process in other states?

I've never tried in other states. But on an absolute scale I found it ridiculous how many gotchas they put in place to keep you out of court. I remember sitting there watching so many people get told by the judge "you forgot to file proof of service" or whatever and get their case thrown out. And it takes a whole day. How many tenants can easily get a day off?

If I were a landlord I'd keep every deposit no matter what.

By gotchas do you mean folks who misfile their paperwork, or that there’s actually hidden paperwork brought out after a proper filing?

"misfile" yes. But it's amazing how easy it is to do that. This isn't like the DMV or a passport where most people can get it right after a couple tries. You really need to be on top of your shit to win in small claims court.