HGSE pays for the visit (airfare, hotel, food) if you are selected for an interview. However, invites have already gone out by now for sure folks. The admissions office is probably telling people to wait until the 22nd in the event that a few prospectives decide to drop out of consideration, but we all know that this is extremely unlikely. If you believe the FAQ on the Ed.L.D site, it says that interviews will be held on February 28 or March 1. Given the fact that most of the people interviewing for these spots are in high powered positions, I'm sure HGSE plans to give them at least 2-3 weeks advance notice so they can make the necessary arrangements at work.