Admiral Nelson said:Get Off My Lawn said:
The appropriate consumer protection may be similar to gas stations being limited to 1 price change per day: a law that specifies if you sell SKU'ed items you only get to change the price once a day.
Plumbers charge a lot more to come to your house at 1:00AM than they do 1:00PM. I doubt they like that law.
labor is not the same as a single product (like chips you'd buy at the store).
Also, the plumber will tell you this before they show up, you're fully informed before you buy his labor.