Who doesn't like a good sale? To be honest, It is very rare of me to buy anything that's not on sale - well that goes for mostly clothes. With food, you have to buy what you have to buy. What is it about us wanting to get a good deal? My boys are drawn to this as well. If they see an ad of "buy one get one free" they are excited to have something free. But don't we all know that truly rarely is anything free. BOGOF is simply jacking up the price and then offering one of them free.
I'm not that skeptical. It is entirely possible that sometimes people will give things away in their quest to promote their products. I'm still, though, of the mind that there are no free lunches! Someone pays.