These are businesses where the knowledge gap is so wide between the service provider and the client mixed with the life or death need of "I need to flush" or "I need heat in the winter" that people routinely get fleeced.
Basically means you're about to be hit with a $500-5000 bill for what is likely a $50 part + 30 mins labour.
Gross margins don't grow, but they are monsterous.