Hi Michael, I would agree that there are a number of very reliable Spyderco dealers selling on eBay. Like you, I don't understand how some of them offer the prices they do. I know one has commented that it's a way of attracting business and, having worked in retail years ago, I am somewhat familiar with the "loss leader" concept (offering something below cost to get folks into the store). But I find it hard to believe that works on the internet, at least to the degree it does in brick and mortar sales. On the internet, your competitors are only a few mouse clicks away, and it's so easy to do comparison shopping for each and every item.
But, if it works for them, and it seems to since some have been around for a few years, then who am I to argue with a good price.