They're not expensive, they're inefficient in terms of water use. Which means they are a non-starter for national retail in the US because there are a few desert states that have captured federal regulation which mandate ever decreasing water use because that's what those desert states want.

Some poor schmuck in "basically Vietnam" climate part of Arkanas has to go to work and fix waste plumbing that's full of deposits from low flow urinals, get home, throw his clothes in a washer that won't clean them because it's trying to sense the bare minimum water it can use (which is too little for anyone who does work outside an office) and then shower under a POS low flow shower head, all so some jerks in the desert can feel like they're saving the planet.

State water situations are diverse. This is a textbook example of something that should not be regulated federally.