I'm not sure that I buy this. It's not simple to make a bespoke appliance like a dishwasher that's better than a very high end mass produced one. Where did you get the idea that this happens from?
Cathode Ray Dude on Youtube talks about this in his videos about the Niveus media center computer https://m.youtube.com/watch?v=Y2OPrGBxkD0
The rich do not give a single fuck how it functions. They have never even thought about that or considered it. If they bought a dishwasher that sucks at washing dishes, their staff will deal with that. If they bought one that breaks after a few months, it will be replaced and they probably will never know. They haven't even stepped foot in this house in months anyway.
The rich are not discerning purchasers because they do not have to be, and they think their time is way too valuable to care about simple things like "Am I spending too much on this" or "Will this widget actually work as advertised"
As other pointed out, they often just have the mass produced appliance if they are not trying to show off.
Custom wine cabinet? Sure.