Why is Step-Up Calculator charging! full tax on Step-up card instead of computing tax on the increment?  I would end up paying tax on the original card and than again for the full price of the Step-up card?? I only end up with one card.

I get it now.  Unfortunately I have to choose against paying more than $100 tax on a $280 transaction.

I believe that, just like trading in a car, you're actually saving money on taxes.  Why? Without the step up program it would go like this:
Original GPU purchase: Pay sales tax
Sell original GPU: Pay income tax
Buy new GPU: Pay sales tax
 
With the step up program you can avoid the taxes on the sale of your original GPU.
Or you can keep feeling like you're somehow a victim.  Up to you. 

This is not only for the State of California, as tax is paid to the buyers state and based on local tax rates where the buyer's shipping address is located. Due to how the Step-Up works, it is considered a new purchase and therefore, we are required to collect tax on the states behalf, based on the full value of the upgraded product. Living in tax free states, like Oregon or Delaware does have it's benefits, in that regards.