The service department at a dealership and every indy shop works hourly. Meaning you pay for the time at a set hourly rate. Then you also have to pay for the parts.
So, not quite sure you think the "mark up" is. Parts mark up is different subject from paying for labor. BMW dealers are forced to use real BMW parts, those have set prices. Yes they are going to be higher, but the quality is higher and much better controlled than aftermarket parts

If you can't do it yourself you got to pay some one else to.

Removing a complete dash is quite the daunting task for most backyard mechanics.

And the dealer service adviser just looked up the times for each mount and added them together. The service adviser does not know how to work on a vehicle or realize there is overlapping labor.