I actually have two apps in the store at the $30 and $50 price points. They're both in a very niche market and we do quite a bit of very targeted advertising.

I actually have two apps in the store at the $30 and $50 price points. They're both in a very niche market and we do quite a bit of very targeted advertising. Based on the tests I've run and analytics that I have in place, we're getting an approximately $20 (net) return for every $8-10 spent (if we spend too much, the return drops off sharply). It's a bit difficult to get exact numbers since there isn't complete tracking all the way through the sales funnel. We do know that if we stop advertising, sales start to drop off after about a week, and drop to our pre-advertisement levels after about three weeks. Advertising does work for the app store, but I would guess that it only works if the goal of the advertising is to get targeted people for a particular niche to know that your app exists. *edit: clarification