Online Travel Booking and Bidding Agencies - How can hotel discount sites be so different?

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?

:confused:

I think it depends on how many rooms they purchases in advance.

So if the site that you mention has higher discount then most probably they've purchased more rooms in advance in those hotels than other major hotel sites ?

Think thats how it works, but I could be wrong.

This online agency may have a "preferred supplier" arrangement with the hotel company, giving them access to better rates than other sellers.

How is it possible for a website to give such a big discount on a room, but a lesser discount on another site?

:confused:
Welcome to Capitalism. Blocks of hotel rooms are traded on the open market just as are pork-belly futures or gold bullion or Metallica tickets. Sometimes the price of a given commodity goes up or down for no reason. In other words, Your Mileage May Vary.

In my experience most hotel booking sites seem to have almost identical prices for most hotels. The opaque deals being the notable exception.

With sites like www.hotelscombined.com and www.kayak.com which compare the price for the same hotel at a bunch of different sites, it's easy to see the differences among different sites.