The PADI Nitrox course costs $150 here, often they are offered for $99. Courses are different prices in different parts of the world, due to the variations in boat fees and other associated costs.
Since the PADI Nitrox doesn't require any dives, I don't know why this class should cost $250 (if it's only classroom instruction)?
Unless this shop is including a dive or two as part of the training. If so, then the $250 amout seems reasonable.
There are reasons shops charge what they do, it never hurts to ask.
This may be the special high intensity training, PADI variation of the Nitrox training. ;-) You never know.
-Mitch