They can't charge that much or people will do their own plumbing. It's fussy, but most routine things aren't too hard to do one step at a time. Sometimes you get a new faucet with an internal leak though, experience might have helped diagnose that without taking everything apart 20 times. Sometimes there's a big job like replacing a lateral, which is yeah, time to hire a pro.
In New Zealand, water work is regulated so only a licensed plumber can do it. The prime minister was once investigated by the Plumbers, Gasfitters and Drainlayers Board for installing her own toilet. Her punishment was having to apologize :P
