According to the DoT stats released on Thursday, IAD domestic fares are very high - second only to CVG. The top five, in order, are CVG, IAD, MSN, IAH and EWR. United has three of the top five locked up as fortress hubs, which helps explain UA's financial success over despite its recent troubles.
http://www.rita.dot.gov/bts/press_releases/bts036_14
http://www.rita.dot.gov/bts/press_releases/bts036_14