In the insanity that is the Match students must interview at 10+ places around the country in order to get a residency. Many spend upwards of $10,000 in addition to medical school for travel expenses.

Fourth year is relatively flexible because students must travel for interviews, and there is an insane amount of vacation and 'slack' rotations available to help this.

The whole damned fourth year is a ripoff, and become more so each year the 'match' become more competitive.