Thank you for getting back to us, @casimoran. 

When you import an item with the same name and let it overwrite all the values, this will merge any imported Product/Service, but will not affect the cost, QTY, etc.

For more information about this, see this article: Import products and services from Excel. 

Let us know by leaving a comment below if you still have questions. Please know that I'm always here to assist. Enjoy the rest of the week.