I have seen only independent Dommes for a long time now but I did start my submissive journey at NYC's then legendary commercial houses. I thought, in some cases very mistakenly, that houses would be safer for me when I was just starting our. Fast forward a few years, and I was committed to sessioning only with Independents and have not visited a commercial dungeon in a long time.
In my experience, Independent Dommes priced their skills and time accordingly and did not want to rely on the generosity of clients. Independent Domme websites would often note that tips were not expected but were welcome while others might say that the Domme would rather have a gift of some type rather than a cash tip. I would think that with rates now averaging $400 an hour that tipping an independent Domme would be unnecessary. Not to say that the rate isn't justified after years of languishing around the $200 - $250 an hour range. The value of anything: service , goods or property is most accurately determined by what in fact the market will pay for it. Since I haven't seen any rate reductions, I am assuming that there are plenty of clients who value a skilled independent Domme's time to be well worth $400 an hour. Or more!
I did usually tip one amazing independent Domme whose hourly rate was below market. She sessioned from her home with an amazingly well equipped dungeon and she was extremely skilled, especially with very heavy bondage scenes. She was also very generous with her time, often going beyond our usual 3 or 4 hour sessions. Other than that, I have not tipped though there was one other Domme i saw many times when she was touring in my area and while I didn't tip her, I did often take her out to a great dinner at her request/suggestion when my session was her last one scheduled.