My suggestion is that we could have trade signs above a donation chest, and when the user paid to the sign the chest would /codify <whoever paid> This way we could sell enchanted tools/bulks of different items automatically. Plugin: None this would have to be custom coded probably.
It would be 1 item for each chest, if you put multiple items in you would expect the person to take it all.
its still a hassle. you would have to relock it everytime because they would still have access the next time you wanted to use it.