Can you post your age?
I'm guessing 16. You don't seem to have a grasp of economics yet is why I am asking.
You're overestimating by a couple years, I think.
Like I said, developers making any sort of decent application are going to abandon the Installer distibution very quickly. You can get your application up and running using a free, well documented SDK from Apple, and then for $100 upgrade your account if you think your program is worth ANYTHING at all. Some testing on real hardware and waiting for Apple approval and bam, you can market your software to millions, not thousands, of people.
If you write something that you think is even remotely useful you can charge $.99 and be turning a profit in a matter of days (the 143rd download of a $.99 app turns a profit for you). Installer is going to be left with the dregs. Junkware, stuff not allowed by Apple's licensing (which does include GNU/GPL material, so there will be useful utilities made eventually), pirated software, etc.
There's just very, very little reason to distribute software outside of the App store. Apple saw to that by making the SDK free and making free applications an option.