I'm not saying that this won't be an interesting thread, I'd be as interested to see the results as anyone, and as my apps have only been on there for a few weeks, I can't tell yet. But trying to measure the effectiveness of a programming environment by the income of users that are prepared to tell you is fraught with danger.
As with any market, putting the apps on it is not even half the battle. If you wan't it to be a success you have to treat it like a business with marketing (outside of the market) to get interest in your specific app.
It's going to depend on the uniqueness of your app, how many free versions there are and if your app is that much better than the free ones that people are willing to pay for it, how good it looks, how well written your write up is, how much time you spend pushing it to all that will listen etc. etc.
It took me about 10 weeks to write my first app (although it's pretty big in terms of what it has to do) that included learning enough about the android environment to be able to get it to work as I wanted it to, and that was quite a few hours a day, more than if I was working for someone else. In terms of time, I invested far more than the cost of buying B4A. Will I see a return on that time? I hope so, will it be this year? I doubt it.