Two things:
- your 18 year figure is inaccurate, I know people who have made it to the top of the pay scale in half that time
- GS-15 step 10 is not the cap for a role like this one. this is scientific/technical expertise, which is 20% higher ($220,200). Not to mention awards.
https://www.opm.gov/policy-data-oversight/senior-executive-s...