Well the ItemStruct (ItemList actually) has a Price integer. I just added the price/cost of the item there, then pulled it from the MakeInventoryStruct or something (you will see what I mean if you follow the OnUsed functions, when loading the item info). Regarding the canbuy, you will have the price of the item, and already have the Gold currency in the Kit, so its just some simple substraction and check if user has the money, etc. I’m quite sure you’ll make it. 
You will also have to remove the part (function) that removes the item from the container (in your new functions) so when people buy the item, it will not disappear from the container.