This feature (or lack of) has bugged me for some time now.
Think of it this way, you're quitting SK. You want to cash out. But wait, you can't. Why? Bacause you bought oh so many costumes.
Or maybe you put an accessory on that you later regret? (Been there, done that.)
What I'm suggesting is something not dissimilar to Name Change Tickets.
Think of it like this, you head over to Bechamel, buy an Accessory Unbind Ticket and pay a measly fee.
Maybe go to Kozma, then buy a new item, Costume Unbind Ticket and pay a larger fee, much like Name Changing.
It could even have a time-release like the name changing, maybe only unbinding one accessory per 30 days?
I know there could be problems, but for this system to be implemented would help a lot of people, inculding me and a few people I know.
Now, costume unbinding may be theoretical, but an accessory unbind ticket isn't impossible.
Maybe, if there's only a few of certain things, it would actually be beneficial to have a way to sell them when you quit. E.G. Hacked/Baleful Aura.
If nothing else, just post your input on making this work.
If your intent is to "cash" back on the items you've bought, implementing an unbind option is not what you want to do: all that will do is allow everyone, not just you, to unbind their cosmetics. There are a lot of cosmetics of any given type in the game, having them unbindable would seriously dropping the price, perhaps even to a point below the unbind price, completely rendering the purpose of this suggestion useless.