I was looking around for probably over 2 years for an easy way to setup a server shop without using scoreboard, because I'm lazy and stopped using bukkit.
I couldnt find very useful info out there for a long time but I recently stumbled across an old post (will link if i can find it) that had 2 commands for a command block chain. I updated and messed around with it and came up with a vanilla server shop concept. Here it is for any who have been looking for something they could do without plugins or scoreboard or data.
Regular cmd block into
chain conditional cmd block
1: clear @p <item> 1
2: give @p <item(s)> #
(Note: make sure the item used to buy is always a quantity of 1 if you care about balance.)
use 1 prismarine shard as a trade for 1 exp level and vice versa.
Primarine for all level 3 enchant books and rare single or double level enchant books, prismarine brick for level 4 enchant books.
Have a refund block for any enchant books.
I hope this helps someone out there like me who has been contemplating this for the past few years to no avail, until now.