Free Sunglasses: A Business Model I Don’t Understand

Two years ago I received an insert with my Runner's World magazine about free sunglasses. The company claimed that they were new and were trying to build brand recognition by giving some initial sunglasses away for free. I could pick up to four pair and only pay shipping an handling. I found three that I liked, and the total S&H was about $20. Two the three pair broke within a few weeks, but I still have one pair that I wear sometimes.

Fast forward to today. I get a flier in the mail from ActivaBrands (which wasn't the name of the original company. I remember it started with a V). The flier looks pretty much like the ad from two years ago, and it's the same deal. Weird. So I begin to wonder… Is this just a coincidence? Is this a competitor doing the same thing? Is this the same company re-branding itself? Are these Sunglasses just a few cents to make, such that the "shipping" fee actually turns a profit?

I open up a web browser and search for free sunglasses and I find lots of sites offering them. Why? What am I missing about this business model? Some of these sites claim that they have overstock sunglasses that they would rather give away than pay to destroy. But I keep thinking that if I was a sunglass manufacturer, and year after year I was overproducing sunglasses that I had to give away for free, I would cut back on production.

My best guess is that either:
1. Sunglasses really are dirt cheap to make.
2. Once you get your free sunglasses you get a bunch of other junk mail.

Does anyone see something I'm missing, or know anything about this strange business model?