Normally, when you hear this, you should be aware! Most of the time, you pay more for the first product, so they can easily give you the next one for free.
But sometimes, it's just as they say. I wanted to buy a new pair of glasses two weeks ago, as my old specs had kissed the surface of the road when I fell with my bike some time ago. So we went to the optician where we usually buy our glasses. The owner, who knows us well, immediately said that I could pick two sets for the price of just one - not only the frames but glasses included!!! If you know that my glasses cost far more than even an expensive frame, then this is really a promotion. I picked out two that I liked and only paid for one. Seeing this opportunity, my sister also bought herself a pair of new glasses and one pair of sunglasses.
We got a message yesterday, to tell us the glasses are ready so we are going to collect them this afternoon. Now I'll be able to choose which one to wear, according to my choice of clothing!