In the event system there's the 'Open Shop' node for buying and not buying. I connected 'Bought Something' -> 'Spawn Prefab'
However, I can't know what particular item the player may buy so specifying a prefab here can be disastrous, unless I make 1 shop per item so I know for sure what item will be bought. Also the amount purchased is another factor. I'm sure someone has already tackled this so please share your advice while GIL is gone. Thanks