I do think the cycling market has a big enough audience with money for them to pay a pretty penny for this. How many brand new BMWs or Mercedes have you seen with a bike rack and a expensive road bike strapped to the top? Yes something like this won't get GTO money because for every sports > cycling > track cycling fantastic there is, there's probably 10,000 car fanatics and let's face it, pretty much everyone loves car porn!
I almost get the feeling high priced items seem to be almost a taboo subject in the fixed-gear world and some people feel intimidated by something so expensive, they beat it down. I don't know the rarity and how many they made of these, but even if this went for the full £7k, I still think something like this should be worth more.
I think asking the seller about how much of a profit he earn't of this is none of anyone's business but the sellers, I hope the chap picked it up for nothing and is making a killing on it!