Anecdotally, my uncle did this back in the late 80s to 2000s. Towards the end he would make AUD$400-800k a year (depending on how many jobs he took on) which was great money for someone who got into it in his early 20s after dropping out of high school.
The catch was the pressure of the environment, needing to be physically in peak shape (my uncle was an anomaly in lasting in the job until his late 40s), and the danger as he had several colleagues die on the job (worst I heard was due to the operators giving the wrong gas mix to the chamber). My uncle also definitely is a crazy man with a few screws loose, so that part checks out
The catch was the pressure of the environment, needing to be physically in peak shape (my uncle was an anomaly in lasting in the job until his late 40s), and the danger as he had several colleagues die on the job (worst I heard was due to the operators giving the wrong gas mix to the chamber). My uncle also definitely is a crazy man with a few screws loose, so that part checks out