I haven't a clue, BusyBee - but I have been wondering exactly the same thing myself.
As you said, they could have been allowed to bring in far more with them this year. I don't think they have been buying them with their shopping because they haven't had enough money! They do have access to cigarettes in the Prize Room, I think, but they're not supposed to take them out of there.
Sorry I'm not much help, am I?