Q7 Indication for Brake pads

[olympiakos]

The indication that my Q7 brake pads needed to be replaced and I took the car to the Audi shop. They charged me with 510 euros. Is this normal?
The receipt said

Brake lining, 2 pieces, total price 360 euros
Sender, 4 pieces, 70 euros
brake pads, front and rear replaced 80 euros

I thought they would only change the brake pads. I have no idea what brake lining or senders are. Please help.

Thank you

[shazoo]

yes there are sender say it wire harness when your brake pad friction material left approx 3 to 4 mm vary( menufecture to manufacture) a light comes on the dash to inform you to go your center to replace brake pads ,hope clear now