I really doubt that gridseed miners are doing anything to the prices. They cost much more per KHs than GPUs, especially now that Newegg has lowered gpu prices again. I know people are still building mining rigs as fast as they can, I'm selling thousands of usb risers a week. It has slowed down some, but a lot of people are still getting started.
Don't buy anything from newegg, their service is TERRIBLE and their prices are absurd. If a card costs 500 on Newegg it will very likely be $50-100 cheaper from other online stores with better service - check superbiiz, microcenter, etc. I recently did a comparison for several key mining items and found newegg had the highest price of all the retailers I looked at for every single item I was checking.