For something like a single platform utility, the burden is relatively low because the number of things that can break is bounded (as long as public APIs are used, private API usage is another matter). With a Mac app like Magnet there’s one time each year chance of breakages occurring is high (new OS release), which devs are given several months ahead of time to find and fix.

Multiplatform apps obviously multiply that burden, with some platforms being more problematic than others — e.g. Android phones sometimes have weird per-device-model quirks that apps need to work around, which is not something one typically sees on Windows PCs, iPhones, or Macs.

Anything with an online/server component unavoidably needs to be babysat to keep running and secure, and the more functional that component is and the more surface it has exposed the more vigilant one needs to be. There’s also hosting costs, which can be quite high in the case of an independent dev who relies on cloud services to make up for lack of resources.

Which is all to say that it makes sense that a Mac-only tiny utility could more sustainably be a cheap one time purchase than many other types of project could be.