Hello I've added a patch i'd be greatful if you could have a look at it.
I have some additional plugins that require these hooks in order to work; then I can publish the plugins for extended GUIShop features.
I've added a few hooks that are needed in order to be able to customize the pricing behaviour of the shop, and also to be able to receive notice when a purchase has occurred.
Note that instead of pulling item prices directly from the `ShopItem.SellPrice` it now pulls the price from the `GetSellPrice` method...this allows price changes to be injected without affecting the original value. GetSellPrice has a hook which allows other plugins to set a different price (such as if they want to make it cheaper or more expensive for certain players etc...).
Let me know if there are any problems and I can address them.