I personally find the polished UI across macOS/iOS/ipadOS and web well worth the expense. I encourage you to watch the videos to see how the UI is both fully GUI tailored to the platform AND is also Text based, so almost all operations can be done while typing inline.

Yes I use Apple to sync the files between the NotePlan apps.

And I use my own tools to keep my NotePlan text files sync'ed to my KDE Linux Workstation where I can edit them in VSCode.

I won't say $100 is cheep, but then again I paid over $150 a year (more like $400 today)for a MSDOS Word Process in the 1980s.