Was the photo sold by Gursky or by a private collector if it is the later gursky won't see a dime from the sale, the same thing with Sherman's selfportrait. Gursky's photo is not my taste but tastes differ furthermore the art market has nothing to do with art and everything to do with the market. Art is sold like stock and just like the stockmarket it mostly produces bubbles created by some selfserving individuals. Never forget who Damien Hearst's best costumer is the answer is simple Damien Hearst. He buys most of his works and creates the illusion of being one of the most expensive Artists in the world, while in reality he buys the stuff himself basically he's a fraud. I doubt that Gursky buys his own work I rather believe that the market creates artist no matter what the artists does for the simple reason to have something to sell.
I'm guessing that's why it's called the art "market."