Z Inventory Manager

WordPress Inventory Management Plugin

Inventory Stats Pro

This feature is available in Z Inventory Manager Pro.

Keep track of current quantity, average cost and price, history of item movements.

There is a nice page showing various useful details about your inventory items performance. Go to Inventory, choose the item you are interested in, then click the Stats link in the menubar.

You will see the total number of purchased and sold items, and average prices for purchases and sales.