When Customs and Immigration merged into ICE, the legacy Customs investigators were GS-13's (pay level) while the INS Investigators were GS-11's.
Since the the Feds could not demote the GS-13's, the GS-11's got promoted to GS-13's.
The INS Supervisors the were GS-12, GS-13 and GS-14 got promoted to GS-14, and GS-15 to match the Customs Supervisors.
This cost billions which ICE had to borrow against it's future budgets to get.
It will be a few years before ICE has any real money for investigation other they terrorist stuff.
You inside insight is quite valuable to keep these discussions at the factual level.