I'm using odoo version 11 and I notice every time I modify the price of a product (maybe the first time?) and afterward create a purchase order or request for a quotation it seems the vendor price gets created by odoo automatically. Is this normal behavior, and if so does anybody have a suggestion where the code is located to modify this behavior.

In our odoo system, we made modifications for the purchase order to directly list the cost price instead of the vendor-specific prices, however, this automatic saving of vendor price is interfering with our workflow. If anybody has any suggestions where we could modify this behavior I would appreciate your input.