I would think that you would not be allowed to deduct the full $500 because you are getting a service — the ability to "skip the line" and grab a graphics card. You can only deduce $500 - FMV of that service, which a reasonable person might say is the difference between the street price of the scalped non-DWB cards and the DWB cards.
If the street price of the scalped cards is higher than the DWB edition, then you would not be able to deduct anything.
This would be for people who want to pay the market price, but who don't want to participate in scalping. If you'd rather wait, then you're not the target market.
I think AMD/NVIDIA are stupid (in a capitalistic sense) for selling their products well below market price, and leaving money on the table for scalpers to collect.
Otherwise I'd rather just wait for supply to become available and donate the $500 outright.