from what I'm told it's the labor involved in removing the rotors. From what they tell me (and I have no choice but to believe them) they have to disassemble the hubs and such to get the rotors off. they say it's a 4 1/2 hour job for the front, and slightly shorter for the rear.
Maybe they are just jerking me around, I don't know. I mostly trust them as they have been working on my Jeep for a few years now.. but you never know maybe they see the land rover and their eyes turn into dollar signs?