Where do you find these plumbers? When we owned our house, we never were able to find any contractor that was reliable, upfront about costs, etc. Hell, getting them on the phone and to show up was hard enough.

Word of mouth from neighbors and colleagues, mostly. I mostly DIY small things around the house, but when I have a plumbing task I can't or don't have time to do, I've had good luck in calling those plumbers, getting an upfront quote (often, "here's our trip charge and hourly rate, and a toilet repair is going to be less than the one-hour minimum and around $75 in parts")

The reason I do it myself is that $75 in parts is actually $20-30 in parts and I can order parts and then do 45 minutes of plumbing work faster than I could figure out what plumber to call, arrange a time, and then stay home to let them in.

Those plumbers probably don't have to deal with a "not invented here" cistern and related plumbing with bespoke thread pitch and piping diameter either.