Given the amount of applications on the app store, it is as hard to find anything as anywhere else.
Plus, people are selling desktop applications since the dawn of home computing, nothing new there.
I seem to remember people were selling software for the Mac before the app store came along.
Im just saying your giving up a major marketing outlet if you arnt on the MAS. Of course you can go it alone, but since it is a MAC app, that would be foolish.