Way too expensive
Yes all these water cooking setups are crazy expensive.
You can buy some GPUs that are already water cooled however unless you plan on only using 2 GPUs max then the entire setup will be bulky.
Basically GPUs are quiet in general unlike ASICs. As long as it's open air and not reference style they don't make too much noise either way.
Exactly, the production cost itself is quite high. But that allows all 8 GPUS fit into a compact box (45,9cm*63,5cm*17,5cm), with high quality parts (Asus, Noctua, Chieftech), no overheating cards and no disturbing sounds.
As to the open-air mining, admit it, there are not too many "cryptopeople" who can do that in their city appartments )