Popcash is a popunder network for webmasters/advertisers.
Tested popads and the cpm was at $0.9, the only thing I didn't like was the displays, they were much lower than what I usually get from AdSense given that popads only give 2 displays per view. I usually get 10p more views from AdSense than from popads, the minimum bid in the code generator was $0.0003. Maybe I should have lowered it more?
If you're on a small budget, don't buy traffic. Even for a relatively cheap format like Popads, you'll have to shell out a lot of money to find a profitable campaign, especially if you're new to paid traffic. Plus, you have to pay for some tools (spy tools, a good tracker...), you need a way to filter out bot traffic (popads have a lot of it). I made the same mistake as you did when I started doing paid traffic when I had a reasonable budget, so I don't recommend it.
Every day my site gets hundreds of useless clicks from popcash.net. If you are one of those who buys this "traffic", know that it is 100% bot traffic. Definitely not human, just a referrer spam, that's all. Don't waste your money for nothing. Added to Google Analytics blacklist