i believe there is a larger commission on LCD's also, they are backed by more companies, and in the past were much cheaper to ship (due to lighter weight and lack of glass)
still actually if you care to look up weights now of days, most comparable sized LCD's weigh almost as much as plasma's at the same size, like I said, panels on LCD's are shifting a bit to get better contrast and color performance and improve the viewing angle, but at the same time it is killing some positives they used to have (no glare, considerably less weight)
also, FYI for everyone, plasma's and lcd's are basically on par now in terms of and their half-life's are rated about the same
negative mentioned above that is true is they do use more power than LCD's, but otherwise most other aspects are on par, except for the fact plasma's still have a much better PQ over lcd's
and agreed, don't skimp out a few hundred dollars on a tv, and do actual research on such a large purchase, in store people know jack shit, look the stuff up online
a nice little review site is cnet.com
and like i said, in terms of crazy consumers who either work in the industry or are obsessively anal about picture quality, check out avsforums.com for people's thoughts on models, issues with certain models, fixes, etc, etc