As an OSS maintainer, $20k wouldn't help me enough unless I was retired. The issue is not money (or not just money), but time. If a maintainer has a full-time job, they may not have time, and developers/maintainers tend to have full-time jobs, so...
Now maybe one could build a career out of OSS maintainerships, with work/time funded by lots of donations much smaller than a salary but amounting to a salary.
I was thinking more of a fix to the issue of "who the hell's maintaining this package our distro/service/whatever is based on" than a way to make money. The bigger projects (like the kernel) and vendors (MS, IBM/Red Hat, Canonical, Google, etc.) all have a vested interest in knowing the actual identity and basic personalities of people who maintain the important packages. If maintainers avail themselves for a weekend at a conference twice a year (or maybe even a lighter commitment like a few short meetings with a manager) they get some resources for their efforts. The flip side of this, of course, is that these organizations will prefer to include packages from maintainers who agree to this arrangement over those who don't.
Furthermore, these organizations are in a place to put experienced, trustworthy contributors on projects that need maintainers if need be. If Lasse had been able to go to, idk, the Linux Foundation and say, "Listen, I'm getting burnt out, got anyone?" and they said "Sure, we've got this contributor with an established record who would love to help maintain your project", none of this is happening right now.
Now maybe one could build a career out of OSS maintainerships, with work/time funded by lots of donations much smaller than a salary but amounting to a salary.