Please guys, don't make a blanket statment, about getting ripped off. There are good shops, and bad shops. There are good techs, and bad techs. I am an ASE certified master auto tech, with A/C being my specialty area. By federal law I have to be certified, Also I am required to have a recovery/recycling machine for every type of refrigerant I work with. R-12, R-134a, R-22 (i do RV's also), and a recovery only machine for contaminated systems, (when someone mixes two different refrigerants in the system. Such as adding R-134 when the system is not empty of r-12, or adding r-22 to a system that does not use it. There are a lot of nightmares out there for the tech. Each recycling machine costs between $3000-$4000. Then I have to buy a identifier($2000) so I know what is in the system, and can use the correct machine. There you go $15,000 just to recover what is in the system. I have about $2000 invested in leak detection equipment. Each type detector, has advantages and disadvantages. How about a scan tool at $3000 to "see" what the computer is telling the A/C. Did you know if the engine temp gets too high, even if the engine does not overheat, the computer will shut off the A/C, to protect the engine? There is a lot more investment required, but I hope you get the point. PS this does not even figure time and money for continuous training.
are you sure that was r-12? It could have been "FREEZE 12", that gets charged as a liquid, since it is a blend. It is not the same as r-12.