This is a feature that is useful especially for inventories. Most businesses need to add inventories to their accounting, and if you add the cost price to all your products it is very easy to get a complete list at the end of the year. From admin you export all products to an excel sheet. Make sure you have both Quantity and Cost price when exporting. Then you can open an Excel spreadsheet and easily multiply the number of items in stock with the cost price and you will have a complete overview of the inventory. The whole thing is done in minutes, and you do not have to count inventory manually. The cost price field is only visible to admin, and not for the customers in your store.
Also, the aim of this addon is to show admin users the cost price of a product, so they don't sell it at a loss.
What is Cost Price?
Cost price is the cost of getting a product from a vendor and into your own stock, ie the purchase price plus any additional shipping costs.