Stop in for a cup of coffee

To be fair, they did a whole lot of stuff to it so it's actually kinda cheap - remember, we're talking about a late model Audi and a proper auto shop here, not the cheapo little shop that always does our old car.

They changed timing belt+tensioner, water pump, alternator belt+tensioner, automatic transmission oil, one of the headlight sprayers and -last but not least - the AC condenser.

On top of this they did a regular 30k kilometer service.

Replacing the ATF is actually quite a procedure. They have to get the transmission to the correct temperature, siphon out the fluid, weigh what they took out and then add the same amount.
IIRC you did say it was about 2k initially and then you added something that was another 150.. so, if it were me, I'd be happy that they didn't "find" another 500 worth of "incidental" charges..