The problem isn't NIMBYs refusing to sell. It's NIMBYs writing the zoning rules so their neighbors can't sell to infill developers either.

Comapre to Massachusetts. We have a law against snob zoning. So while there is a homeless problem, we're making steady progress because of developers buying people out and building apartments. (Mind you're, they're mostly buying parking lots, gas stations, and mini strip malls and putting housing there. And nobody's eminent domaining anybody.)