Cost for a new carb

I was at a small engine repair shop yesterday to buy some fuel hose. I was looking at their labor rates that were posted on the wall. It said small hand held engine and lawn mower labor rates was $80 per hour. Riding mower rates was $100 per hour. Maybe someone could explain to me why the hourly rate was different? Does the riding mower require a Masters degree? Personally, I think there is some dishonesty here. I know the same mechanic works on both machines.

I guess I should add, this is in california. I am not aware ow any shop rates of $150 in the Sacramento California area. Could be, but none that I am aware of.

Wayne