Where I used to work labor was charged at $75.00/hr and the company basically broke even on labor charges. They had good training and all the guys had vans to drive in with the company logo. But, between loading vans, pre-planning in the shop, and delays/issues, the company basically makes back about what is spent on the labor force and the labor is there to help drive the sales, especially custom sales.
Really, on a big, custom job, a person doesn't just go in and buy boxes. They go in, need a salesperson to help them, then if it is really custom, it goes to engineering, and finally a full proposal is written up. Only 1 in 4 or something like that actually gets signed off on. So, that one customer is paying into the overhead expenses of all the other people who did not buy. If everyone bought, then everyone would have a better price because overhead would drop. But, people don't want to pay for an estimate, they want free advice, then to shop it out.
C'mon, of course it's cheaper to buy online! But, then you want to pay a company cheap labor to install it... and what happens if it doesn't work? Who uninstalls it? Do you expect it to be 'taken care of' by the company that installed it when it isn't their product?
I have no problem with labor rates in the 75/hr range really.