Commissaries are appropriated fund activities. They are not run by a concessionaire but are managed by the Defense Commissary Agency.
IIRC, DeCA receives about one billion appropriation for its managerial staff. We had a five day only schedule here at Fort Jackson during sequester.
The commissary here has real competition; it has a surcharge of five percent (since 1971) but the South Carolina sales tax on food is only one percent.
DeCA prices on fresh meats & produce are still kinda hard to beat.
I heard that with no budget, only C/R’s, that a govt shutdown really will mean no checks for soldiers & grandmothers. Anyone hear differently?