Mac desktop market is 1/10 of that of Windows. There are however multiple "buts". Windows users are more reluctant to pay for software. When they do, they want to pay less. They tend to have less regard for aestheics and well-crafted UI/UX, but those that do will be sold instantly on the app that have 'em.

Regrettably, the percentage of Windows users that do value build and design quality over the abundance of features and low pricing is, maybe, 10-20%. On the plus side, however, this acts as a natural filter and you end up with the userbase that really groks what you make and how you make it. This alone is a huge plus. "Those who like it, like it a lot."

Long story short, if you can take your well-made Mac app and port it to Windows, retaining the polish - do it. It's totally worth it, in all aspect of it. Just make sure it looks and feels native, and it's not an Electron ;)