Costco gets to sidestep a lot of regulations because they technically are a private club with paid membership. The US anti-monopoly laws are also unusually weak.
In other countries, selling a $7 chicken if it's subsidized by the sale of other goods can indeed be illegal.
If you now acknowledge there is a carve out… couldn’t there be two carve outs? Or more?
It seems like you havent thought this through at all.
Do you have some countries in mind where that's illegal?