ALL TESTED WITH SPIGOT 1.8
This will add the command /sellmode to your server, only players with the permission "sellmode.use" will be able to use the sell mode command, once the command is executed any chest that is clicked by the player who executed the command will go through the config and check if the item id is specified in the config, if so it will take it out of the chest and add money to the players balance using vault.
#SellMode sellable_items: 4: '10' messages: entered_sellmode: "&6 You have entered sell mode, right click a chest to sell the chest's items" exited_sellmode: '&4 You have exited sell mode' items_sold: '&6 You have sold %amount% x %item%'
sellable_items: 4: '10' itemid : 'price'
then after the next server reload or restart the new item will now be sellable through sell mode.
Permissions and proof of ownershipPermissions: