Dornbracht Cost, IIRC, about $1500. The plumbing gods were not slow to punish our hubris. Two issues developed. It has 2 small integral check valves. Grit was keeping them open causing hot to flow into the cold. Never could get cold water in the master bathroom sink in normal conditions for a year until we fixed this recently. Had to let the cold run for about 25 seconds in the kitchen as well. Since this fixture is so rare, contractor did not install tile to allow proper access to valves, so he had to hack away at tile beneath escutcheon. The main cartridge needed to be replaced. The problem was that if all 3 shower heads were on, or the valves were opened too suddenly, or the water was turned toward cold, the water would become freezing cold and had to be turned off and on again. This is a $500 part, but was covered under the 4 year warranty. These problems are tricky to track down. A licensed plumber refused to help him with this (we did not know how the hot was getting into the cold, and his experience told him how frustrating that could be to pin down), so my contractor trouble shot it himself, consulting with me several times. Nothing looks better. And now that it works properly it's a joy to have. But beware the high end, and doubly beware the ultra high end.

You might want to try the plumbing forum or go over to the Terry Love plumbing forum and ask that question.

Also have the grohe. I was talked into the thermostatic by the sales person. It's okay, but I could have lived without it. She described it as a must have, but I honestly don't see the big whoopee. Also, I found I couldn't get really cold water or super hot water out of my faucet once it was installed. Maybe this was an installation error, but we like freezing showers in the summer and super hot baths in winter.

The ones with one knob, you are really adjusting for temperature only. The only way to get less water is to go cold. I have had a Delta Pressure-balance system with one knob for years. No volume control, really, unless you don't care about the temperature. The only other way to control the volume is to get a shower supply pipe with a T coming off of it for a handheld. I have a valve up there where I can choose the shower head or the handheld shower. If I choose the handheld, I have another valve on that head that allows me to turn the volume to whatever I want. None of that has anything to do with the Pressure-balance system, though. That is still set at the same setting through all of this. My new system will be a Temperature balance system with three volume controls. I will be able to turn the shower head on full, off or anything in between, ditto for the handheld, and ditto for the rain head. The water heater will not support all three at the same time, but we are a house of grown ups and if we try that kind of shenanigans, we will suffer the consequences of finishing with a cold shower! I usually turn it all off to soap up now. I imagine I still will do that, and the rinse will be faster with the rain head. I am hoping to use less water with the new system, with less time fussing with valves.