Pretty sure it can be done in the car using the OBC, it can on mine.
Some cars (not sure about Audi) can be reset by pressing the trip reset button and holding it while you turn the ignition on. Count to 10 and it resets, but I can't confirm it works on Audi.
Failing that, apps like Carista and Carly or OBD11 can do this and much more for less than those quotes and you can diagnose cars with it in the future. Worth buying one of those devices.