I didn't find the expense to be the big issue so much as I don't see a new-ish device that's capable.
Postmarket OS, for example, appears to work the absolute best on the Google Pixel 3 and the OnePlus 6, and both of those are well past their production dates and are hard to get hold of.
I think they ought to put up a list somewhere of the newest devices they support with at least decent support such as your standard calling, texting, media, etc.