This manufacturer publishes what its codes mean, which is rare and genuinely useful. What a published cause names is a circuit rather than a component: the dishwasher drain code covers a filter, a pump, a cover left loose, a kinked hose and an air gap. Four of those five cost you a visit. One of them is a part.
A number quoted over the phone has to assume one of those, and it will be either padded to cover the worst case or too low to honor once the panel is off. So the diagnostic settles it, the scope and price are written down, and nothing is opened until you have agreed to them.