Not a silly question at all, but it seems they just don't care so they charge what they like and sit back and see what happens. On occasion I buy from a retailer in Sydney, Tri-X and Across, at about $13.00 a roll. That seems reasonable, but I usually buy large quantities from the US, which is still a lot cheaper despite the horrific postal costs.
I really don't know where Vanbar gets it's stock, but if I can import it cheaply...? Either they are ripping us off, or their supplier is ripping them off...either way I'm sure they never sell any film!