It might be nice to have some sort of refund feature in the black market on kitpvp, in case you accidentally buy something you didn't want to buy (of course, nukes, keys, and other physical items probably shouldn't be refundable). It seems like the mana plugin handles both giving and taking mana away, so maybe for just the kits at least, if you right click maybe your perms to the kit will be removed and you'll be refunded maybe a partial amount of the mana you spent on the kit (so you can't exploit buying the kit, using it, and then just refunding yourself over and over again to get lots of kits in a short time).