If you want really cheap mobile traffic, take a look at:
TrafficHolder (Price starts from: 2.09$/k)
and
TrafficShop(Price starts from 1.35$/k)
Why traffic above so cheap? Because those sites buying all kind of skimmed traffic and just filtering it.
Also offer you to checkout following brokers:
EroAdvertising
ExoClick
JuicyAds
Once again I'll remember you that all brokers are auctions, which means higher bid - more traffic you get, but in case if you don't want to spend a lot of money, stay on 2nd(3rd, even 10th place) and you still will be getting traffic.
Good luck!