The reason they do this is simply because there are people out there that have no clue about Macs. Trust me on this, because I've sold two of them in the last 6 months. I bought my first MBA last October (a 2010), paid 780.00 for it. I sold it this past July, and while I had it, the warranty ran out, I dinged it, and I damaged two of the rubber feet, and I still sold it for 750.00 on eBay. I bought a refurb 2010 right after (at the time, I didn't think I needed a 2012), and I paid just over 900.00 for it. I sold that one a few weeks ago for 800 on Kijiji. I finally settled on the one I just bought (a 2012 11" 1.7/8/128).. for now. lol
It just goes to show what people regard Macs as. A lot of people have no clue and tend to overpay. Plain and simple.