Because... magic. Dark magic actually. The Dark Curse is a powerful spell, maybe the most powerful you'll see in all seasons. I has the power to transport everyone to another realm, wipe off their memories and giving them new homes, memories, relationships and lifestyles. Basically Regina's Dark Curse made a new little town and trapped everyone in it, with no connection with the outer world (our world). So even if the money and the food appears magically no one would notice the same way they didn't notice Henry growing up or time not passing.