My hat's off to Daniel James for sharing this information. (article here: http://www.gamasutra.com/view/feature/4046/what_are_the_rewards_of_.php?page=1) I too would like to chip in with some numbers that I recently shared at a talk I gave at IGC Boston. They should serve to back up James' statements as I've seen similar results with my online game (DomainOfHeroes.com), though on a smaller scale as DoH is new and only has about 30k players so far.
I'll break the figures down into Lifetime (8 months) and 7 day (last week). Daniel didn't mention this, but I would add that the numbers seem to get better each month as long-time players continue to make purchases and new features are added that retain/convert newer players.
I'd also like to add that "Sales" events are huge. As in 10x revenue generation. This is why the 7-day ARPPU numbers (no recent sale) are lower than the lifetime ARPPU numbers this week.
Additionally, ads and "sponsored offers" (think TrialPay, Offerpal, PayBuyPartner, Gambit, Super Rewards, etc.) Represent an additional 10% on top of the purchases. Not a huge share, but an extra 10% is nice.
One final interesting tidbit that I've seen is pricepoints. Our microtrans game has pricepoints from $0.99 to $349.99 and about 80% of the revenue comes from purchases at the $19.99 pricepoint. So even though games are pitched as "free-to-play w/microtrans", the transactions can actually be major ;)
Information sharing like this really helps the industry, especially for smaller Independent companies like mine (TandemGames.com).