Mutual benefit from the mining and sales of video cards. Why do not they raise the price of their products if it is so in demand. Therefore, you can say demand creates a price, but now home mining at such prices disappears or becomes minimal.
They already have a graphic card for mining. But the price too damn high for them so they buy graphic for gaming because it cheap and good to be mining too. This thing is bad news for gamers because price already high due the high demand and something like this is off target market.
below this about that news
https://www.polygon.com/2018/1/23/16921356/nvidia-graphics-cards-sold-out-cryptocurrency-miners