Plenty of businesses exist that solely make desktop software for Macs. For big examples, see Panic and Omni Group. For a smaller, more recent example, see Qbserve (whose owner occasionally posts in these forums). For many years, my sole income was from a Mac desktop app (I now have a Windows version too).
The Mac app store started well, but gradually faded away in use and sales. Some of the big names in Mac software have stopped using the app store altogether. This is for various reasons, including rigid sandbox limitations on software sold in the app store, and Apple not permitting paid upgrades. For mature software, paid upgrades is an important part of the business model.
Comparing to Windows how much sales you make with your OS X application?
This is a hard question to answer in general, I'm afraid. It depends on many factors, including the type of software, the existing market, and your relative marketing effort. In my specific case, sales are roughly 50% Mac, 50% Windows, but this is probably because for years, we only sold a Mac version.