Orchestral musicians. It is an incredibly high pressure job. You have to be perfect week in week out. While there are good union protections, if you get on the outs with a conductor, you may end up out of the music. Winning an audition to get into an orchestra is like making an Olympic team. Positions are few and far between. So, if you lose a job, odds are you will never get another. The top ten orchestras in the US make about $110k to $140k. But that is chicken change in places like San Fran, NY and Boston. In mid sized cities like Indianapolis and St. Louis, pay is $65-85k. In smaller markets like KC or Charlotte, pay is $35-40k. Most musicians outside of the top ten orchestras will also have to take on teaching positions and take on other gigs doing chamber music or playing in churches and summer festivals, etc. So, a work week can easily be 60+ hours of playing, practicing and teaching. When everyone is out having fun on Friday night, you are working.
While it is possible to put together a good living if you are lucky enough to get a job, compared to pro athletes and people on a similar level in other professions, the pay for orchestral musicians is chicken change. Getting a salary job in a professional orchestra basically puts you in the top .01% of orchestral musicians. Compare that to what the top .01% of doctors, lawyers, MBAs, etc. make and you can see that these highly talented musicians could do so much better at just about any other profession if they were able to make similar achievements.