How many work hours can they make that kind of money? Every day, all day? I doubt it. Let's see that "$30 to 40 an hour" reduced to an average hourly wage.
There is a Waffle House waitress here who is fat and not the prettiest face who makes a lot of money on tips. She has a keen awareness of what each customer responds to and provides that. With some she is coldly efficient. She flirts with others and can change the mode between adjacent tables. She makes a lot of money and is putting herself through school with it. She says she might just continue to wait tables after graduation. She says there is more money in it.