Well, if you're Backflip Studios, maker of iPhone hits such as Ragdoll Blaster and Paper Toss, your portfolio of ad-supported games earns you $500,000 a month!
http://www.mobile-ent.biz/news/39186/Backflip-Studios-making-500k-a-month-from-in-game-ads
This is in ad revenues only. It excludes money earned from purchased games. These revenues are more than double what Backflip was seeing from ads six months ago. Based on last year's trend, Backflip estimates $2 million in ad revenue for the month of December!
Backflip has 47.5 million downloads on iOS and 5.5 million on Android, though it's not clear how many of those were free and how many were paid. Those installs see around 2 million active users daily and 15 million active users every month, generating 600-800 million ad impressions.

"The worst part about these reviews is they are [subjective]--and their scores often depend on how drunk you got the media at a Street Fighter event." — Mona Hamilton, Capcom Senior VP of Marketing
*Image indefinitely borrowed from BrainBoxLtd without his consent.







