Well, it's been five guesses since my last clue.
The answer is La Venta:
Apparently they're having a huge sale there: La Venta literally means "The Sale" (yes, I know it doesn't mean sale in the sense of 50% off, but rather sale in the sense of a transaction, but it's no fun without a little word play).
Oh, look, they're having a special on stone heads!: Olmec stone heads!
They're handing out religious relics!: It's a religious city state.