This issue is really a concerning, i see that nobody is buying rx 580, the rx 570 is hard to see around but rx 580 there are plenty available and I hear there will be a huge stock coming in of rx 580 everywhere, buying gtx 1070 at exorbitant prices is still the best alternative.
What? The 580 sure is available but at ridiculous prices, and the uninformed newbies watching YouTube sure are buying em. What will happen is going to be the same thing that happens when restocks come in:
1) Bots buy all they can
2) Miners use the GPUs or resell at ridiculous prices
No matter how many they put out, there's always people buying or reselling higher. Nvidia is overpriced as you said but still available.