There is paid commercial software for Linux, like MATLAB or Wolfram Mathematica. But the sad truth is that many companies like Microsoft aren't interested in offering MS Office for Linux. A lot of FOSS projects do make money by offering things like 24/7 support and security updates guaranteed for x amount of time (see Ubuntu Extended Security Maintenance). Also a lot of software is used by big companies that do have an interest in sponsoring the development on something they depend on. Where it be by contributing development time themselves or donating money to the developer fund.
Maybe as Wine advances we'll be able to use more and more commercial Windows software, kind of like what is happening with games. But I'm not holding my breath yet.
There is! CrossOver from CodeWeavers bases on Wine and the company employs many of the Wine maintainers. So buying from them directly sponsors Wine development and gives you access to an improved product over Wine.
Maybe as Wine advances we'll be able to use more and more commercial Windows software, kind of like what is happening with games. But I'm not holding my breath yet.