I was told about a website that could help me find the best prices for hotels, called "Self Plan Travel". I was surprised at the big difference in prices between the different booking sites (i.e., gtahotels vs. hotels.com vs. lots of others). Does anyone know if there is a "catch" to big difference in some of the prices? How is it possible for a website to give such a big discount on a room, but a lesser discount on another site?