Features and cost wise i like STEAMSEO.COM their cost as CPI 0.05$
Features
self manage portal
NO sdk required
low start budget 10$
live tracking
24x7 live support our skype: steamseo9
Geo target traffic world wide
big volume
provide white label
options for publishers and advertisers
choice of bid
discount coupon on big volume
options of cpi,cpm,cpc,cpa,cpl
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