I think everyone here is lookin at this wrong.

The training center is one part of the equation. I almost guarantee that the current site and remodel revived the biggest incentives from the City of Denver and the state of Colorado. The rest of this is small potatoes. If I remember correctly the city of Denver offer just north of a Billion dollars in breaks to United. Think bigger than just a training center. All of a sudden DEN is the highest margin airport(the pot Industry definitely helped this but that only part of the picture). The location had everything to do with a better deal overall for Denver not where the training center is located.