Is it a) the FTC has not stopped bad mergers. Too much power over the price of food/gas/etc... in control by 1 company.
Or b) actual price collusion. From my personal research price collusion has become "legalized" through a cottage industry of "price analyst" companies that provide "good guestimates" of what gas, food, etc... should be. (aka realpage is out there for EVERYTHING already we just need to find them).