I have no idea what labor rates are where you are, so id need you to brake down the invoice to see whats up...also have no idea how much freon your unit holds either, so this isnt a definitive answer but hers a few things to look at...
The avg say 4T a/c unit holds around 10lbs of F-22. Here it goes for from $9-$22 a lb retail. However if your A/C held 10lbs and was more than 4lbs low then the guy shouldnt even have put any in it without finding the leak 1st....YOU DO HAVE A LEAK.....freon is not used by the a/c it is simply circulated by the compressor, every drop should be there 100 yrs from now if you dont have a leak...
The new DEMOCRAT passed laws have a level at which the mech is supposed to find the leak instead of just refilling. knowlingly putting F22 into a leaking A/C is no different than just releasing to the atmosphere...
But as far as this guy ripping u off.my bill would look like this..
SERV CALL---$55
Labor---$66
F-22--4lbs @ $11.00
thats $165 + any taxes and i would assume all this IS more expensive where your at than down here in the ghetto of the U.S.A