odometer:
I am aware that DS3231 is expensive, and I expect that other, similar high-precision RTC chips are also expensive.
$15 doesn't seem that expensive to me. Where do you put the "is expensive" threshold?
Are clocks with high-precision RTC chips sold for use in homes, small offices, etc.?
I've never noticed any but I've never looked for them either. The radio ones work great in my house. They are freakishly well synchronized.