This is not possible at this point. By design each product variation item has Additional charge
property, where the difference is entered if there is a difference in the price of this particular variation of the product. Currently, we don’t have possibility of entering the final price in the product variation item.
There is a feature request for this functionality, you can vote here:PITS
Do you want to have your say in the Sitefinity development roadmap? Do you want to know when a feature you requested is added or when a bug fixed? Explore the Telerik Public Issue Tracking
system and vote to affect the priority of the items