There's a lot of unseen plumbing there, though, mostly underground tanks to handle storing graywater (cities have fairly stringent rules about discharge rate, s

There's a lot of unseen plumbing there, though, mostly underground tanks to handle storing graywater (cities have fairly stringent rules about discharge rate, so you have to store and slowly release a lot of water over time), plus (increasingly these days) reverse osmosis systems and graywater scrubbers for recycling. Most of the cost there goes into construction, not components, of course, but it's considerably more complex a build than older setups.