Any kind of dealership is going to make more money selling parts and service than they will selling new equipment. It's a big chunk at one time with the new equipment, but the parts and service have much higher percentages of profit, as you found out, and that's what keeps the doors open.
And as more options become available for parts, like used and aftermarket that you can actually find because of the internet, they have to increase the price on the parts that are dealer only to compensate. I'm not a dealer, but was involved with them, and that was what they told me. Made sense.