I feel that $150 is way too much and would suggest 1 hour of shop time is more than enough. Depending on how mechanical an individual is and facilities available, a DYI assembly is workable. If the person is impatient, clumsy, or can't tell left from right, then someone else should put the parts together. There are several places one can go wrong and cause damage to the lower(sometimes completely destroying it).
When I have my tools out and my hands are cooperating, I can install the parts and stock in 15-20 minutes and hand you a working AR lower. The first one I assembled on my kitchen table having never seen a parts kit before and it took an hour. Keep in mind, I'm a trained engineer and lifelong mechanic as opposed to some one who can't operate a can opener.