My take.....totally unfamiliar with timeshares. You have owned the lease on the unit for your weeks for a long time. The maintenance fees can basically go up at their discretion (only thing limiting the fees is the marketplace of turning owners/future owners off), the release fee is totally made up and the justification of such a fee is two fold: as a deterrent to leave so that you keep paying maintenance fees AND if you do end up leaving and pay a money maker for the resort. I'd walk away and wouldn't feel the least bit bad about it.

It is not at all like walking away from a mortgage. If your maintenance fees and this made up fee were locked in on your original contract way back when then there could be an analogy but I would assume that the maintenance fees always have a tendency to go up and that this made up release fee is a new trend and wasn't even around back then.