An upgrade in my definition is a substitution of one product for another (better or equivalent). I want to base an upgrade on live material pricing. I.e Upgrade Malarkey Highlander to Malarkey Vista. An upgrade product should let me link this product to Malarkey Highlander and Malarkey Vista and make the value the difference between the two products.

Right now, the "Better" option that shows the Malarkey Vista upgrade just adds Malarkey Vista but doesn't subtract Malarkey Highlander which is on the "Good" base contract. This makes the upgrade to Malarkey Vista 10x higher than it should be. Great profit but im not going to sell as many upgrades if we are over charging that much. So I create a product called "Upgrade from Highlander to Vista" and calculate the difference myself. It works but it is not attached to live pricing which is what I want and now I have to maintain that upgrade product pricing. We like to give a lot of options for upgrades so making and maintaining every combination of "Upgrade" or "Switch to" will get cumbersome unless I can link them to the products that are getting live supplier pricing.