Wait a few days...the 6800GS is coming out, and that should lower the price of 6800NU's.
Since NVidia discontinued all 6800's not in the "GS" format, availability will only decline... supply and demand will actually INCREASE the cost of the 6800NU if anything, I seriously doubt you'll see these cards get cheaper as they become harder to find. Anyone seen a FX5900U for $100 bucks lately? Performance doesn't equal cost... supply and demand do... once the supply dries up, prices tend to increase. Current 6800U's and 6800GT's seem to be increasing in cost lately (costing more then 7800's) due to scarcity... don't expect the 6800NU to tumble now that it's discontinued.
The only thing that may decrease in price (if anything does) once the AGP 6800GS debuts might be the 6600GT... but to be honest, since the 6800GS is replacing ALL 6800 cards, it is filling-in a large price-point in the NVidia line-up, so expect all other cards to stay in their same price-range.