http://bitter.io/?r=142150 is a Bitcoin traffic exchange like site that allows advertisers to buy cheap website traffic with Bitcoin. Advertising costs only $1 for 1,000 unique views. You can also set the visitor duration from 10 seconds to 60 seconds and get a discount on higher viewer duration.
I would strongly recommend anyone one who is in need of cheap traffic in the cryptocurrency niche to use http://bitter.io/?r=142150. The only down side to bitter.io is they have about 40,000 active users so you will be severely limited to the amount of unique traffic you can buy.