Oh its free
Have you been shopping lately? Recently I bought a shampoo and it comes with a free gift. Yeah that's how marketing now, its one way of attracting customer to buy buy buy. What free gift I got from buying the shampoo? It's a free comb which you can put in your bag. It's small and has a mirror on it, the comb can be folded as well.
It's very common now, yesterday I saw a shop selling mobile phone as low as $99 but with condition that you need to purchase the model of the phone.
Even food, I come across restaurant that have their menu set like buy this A set and you get a free drink and free soup.
Did I missed out anything?