All these things that I have done

Due in part to being bought up by the worlds greatest cynic (my dad works for an ad agency) I find myself utterly unable to ever call these things - even those scratch cards you get in magazines which now say "Your prize will be worth at least 5 times the cost of the call" on them. And yet I find myself curious as to exactly what the scam is and tempted to call just to find out! After all, they must be making money somehow...