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.
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.