There are many factors, but the primary reason GPUs are unavailable is due to mining demand. The increased DRAM prices only add about $20-30 at most to the average price of a graphics card. So the cheaper cards are starting to see this effect, but the mainstream/mid-range cards should not be $400, and no one should be paying $1000 for a 'consumer' grade card of any sort.
I should add that you as the consumer are not buying in volume. GPU manufacturers are, so they aren't as effected by the increased DRAM prices. Doubled to the consumer, even an 8GB GPU at volume isn't going to show that much a difference. That should still make something like a GTX1080 around $600 (Which is oddly available right this second for $615, but the nicer...