Without studying the site, I'm wondering if the alumni section demands higher prices. Konerko isn't officially an alumnus at this point, but he does have team-giant status.
The price seems a bit high, but I don't track autograph values. I was at a yard sale in Modesto, California, this summer where a man was selling a Paul Konerko autographed ball (something signed by a young Paulie in his Dodger-prospect minor league days) in his driveway with some others, mostly A's. He was only charging $10. This isn't an area where there's great demand, and I didn't need it because I have a ball autographed by Konerko. I could be the only White Sox fan who ever visited this guy's driveway. When I asked about the ball, he started to explain to me who Paul Konerko is.