Ticket prices should be $5-11 cheaper on the airline's website, because you won't have to pay the administrative fees. For example, if you find a $121 ticket from NY-LA, you should be able to go to that airline's website and find the ticket for $116 (I think it's Orbitz which charges $5). What a lot of those sites do is "conveniently not update the database that much" so it might show that you can get a seat for $150, but when you try to book it, you get the "Sorry, it's not available" line. The prices are different because of the charges that the different website companies add, and the fares they search. Orbitz, IIRC, has the most thorough search.