Fares are very variable on this route. I beleive NW flys the only non-stop route and there is very little comeptition. A few years ago, the cheapest flight was always $700. Earlier this year I was able to to it for $350.

O&D is part of the issue as well. There is pretty heavy traffic out of DC on Thursday and friday (congressional delgations head home) and retrning Sunday and Monday.