Cryptocurrency mining has been wreaking havoc on the gaming community in recent times, making it nearly impossible to find and purchase a high-end graphics card. Most cryptocurrencies right now are "mined" by utilizing specifically designed hardware, or Graphics Card Processors (GPU). Unfortunately, these same GPU's that gamers use are being purchased with the intent of mining, and it's had a massive effect on the availability of these parts. Prices have soared, and availability has been near zero in many locations (including online retailers, like Amazon).
Nvidia is aware of the shortage, and made a statement on the issue:
For Nvidia gamers come first. All of our activities around our GeForce-products are directed towards our main target group. To ensure GeForce-Gamers continuously have access to GeForce-graphic cards even in the current situation, we recommend our trading partners to take according measures to ensure they can provide the needs of gamers per usual.
Some retailers are trying to tackle the issue by limiting quantity per customer to one or two graphics cards. This can help keep some stock for gamers who just need one card to build a computer, rather than making a mining machine. It's not a perfect solution, but it certainly helps.
Currently, it's virtually impossible to get a GTX 1070 (or at least, at a reasonable price). The GTX 1070 is one of Nvidia's high-end models, balancing performance for cost making it a very popular buy for gamers looking to be conservative while building powerful machines. Nvidia initially announced the pricing at $400 for a GTX 1070, but the best you can get it for right now on Amazon is anywhere from $700 to $900 plus.