How do I add a custom attribute that changes the price of a product? The catch is that each product has a custom value for ‘Upgrade’ or ‘Discount’. I’ve tried using several modules which work fine but it’s not possible for me to individually customize the prices. So basically as follows:

Product 1, upgrade(+25 dollars), discount(-30 dollars), As Pictured (+0 dollars)

Product 2, upgrade(+50 dollars), discount (-45 dollars), As Pictured (+0 dollars)

All of this is doable for me on a product to product basis, but not as a large import (roughly 500 products with several custom attributes)