Interesting.
The issue I have with bux sites though is that they're not adsense friendly. Not that I would ever use them for that purpose.
However, I think it's a bit of simple mathematics.
The site has around 3000+ members. I would say, of course, not 100% of them are active. So, to reach a click pack of 20,000 visitors, the active members will have to click multiple number of times to a URL. It is traffic, but probably out of 20,000 clicks, maybe 2,000 would be unique, or less. The rest would be repeat visitors.
Anyway, seems like a good way to drive traffic somehow and good prices, too.