Compressors usually last about 11 years for heat pumps units and more for non-heat pump units due to the compressor is only used during the hot months. ON mew units most compressors are factory warranted for 10 years (they know exactly how long they will last). Compressor it's self not that expensive, but 99% of people have no clue how to change them so the mark up is 3 fold... Just like your refrigerator the compressor is the heart of the system and we all know heart transplants cost big bucks...
usually 1/3 of new system or 1/2 of the outside unit replacement...