What is the purpose of cost price and SKU in the product catalogue?

Cost price is the price at which the merchant/admin had bought an item, a difference between the cost price and selling price determines the profit. SKU is a unique identifier in terms of a number or code allocated to an item in the catalog for admin/merchant to identify/map products listed in Yelo with offline stocks or for analytical purposes.

In standard SAAS, SKU and cost prices are entered manually while adding an item to the catalog. SKU is also displayed in order details to the admin.

This information can be useful to you if you are using a third-party tool via integration with Yelo which makes use of this information else it has no use on the Yelo platform other than being visible to the admin/merchant just for information purposes.