On my Campy bike I changed from a standard double to a compact, and I think it was $75 or $100 including labor.
My bike has older Athena, which the LBS loves and says is compatible with just about everything. The guys at the LBS said the shifters could even handle changing to a triple if I wanted.
It seems hard to imagine the newer Campy is less compatible and changeable, so I'd really try to find out why the shop can't switch to a compact without changing everything before dropping a ton of money.
"If Americans want to live the American Dream, they should go to Denmark." - Richard Wilkinson