I used to be a GS-15, Step 5 for a short stint in government while living in SF. I was within $5k of the pay cap due to the location adjustment. Cap was somewhere around $165k at the time. Still, this was significantly worse than my job before and after.

For some people on the team their government salary was a good step up, others didn't necessarily need the money and were there for the mission only. I was there for the mission, but certainly also needed the money.