But how did you know they were making money?

AppAnnie (http://www.appannie.com/) gives some good insight in how well apps are doing.

Gross rank for apps reveals a lot. Any top 25 app by gross rank is doing well by "niche" standards.

Doesn't Apple only let those who have purchased write a review? If so, the gross number of reviews may give some idea of how many have purchased the app (ignoring price fluctuations, etc)

Some developers have told me this is a good rule of thumb, but for others it's way off. Mine # of reviews is not really indicative of how many downloads.

From what I've read it's:

(# reviews * 30)

My apps are more like (n * 100). But that is on Android...