But both machines are similarly capable and configurable with 800FSB 3.2Ghz procs (which are BTW, a good % of the cost of the system). I'm sure the widescreen format brings up cost a little for the 4780. In the end they are almost the same machine, therefore similarly priced.
Mostly, that's the prices that SAGER put on them. Its likely given their cost to manufacture and deliver the machines is similar and they probably have a standard markup. Then again, maybe they throw darts or perhaps i-ching.