First of all, let's stop pretending the Halo fans who first played Halo 1 at LAN parties, and then picked up an XBox with Halo 2 for $250, are all going to buy a 360 with Halo 3 for $460. The bulk of people who bought an XBox for Halo had a $250 price barrier too, as MS dropped the price right away and Halo sales slowly picked up, not all coming in one shot like Halo 2. The same goes for GTA, which was largely bought with a $250 price threshold.
Second, there is no reason for Nintendo to stop the Wii Sports pack-in. People think of it as a $50 value, but the cost can't be more than $2. Why risk it, when it has obviously so far been the key to their success, and they probably get a better profit margin the way it is now? Furthermore, I can't imagine Nintendo cutting the price anytime soon, considering how high their sales are with continued supply problems.
Third, the immediate effect of a price cut is often overrated. I think it would be difficult for anyone to look at weekly or monthly numbers for any past system, and pick out the months where price drops occured. The 360, however, is at a unique point, where there may be millions just waiting to come on board with Halo 3 and GTA4--IF the price is right. If MS doesn't drop the price in time or at the right time, those could be lost sales. But a reactionary price cut could not counter that. Nintendo's big games won't get as much of their sales up-front, and Sony doesn't have any exclusive games with that appeal. A $50 Wii price cut or a $100-$150 PS3 price cut would have the same immediate effect as the recent $30 PSP price cut.
"[Our former customers] are unable to find software which they WANT to play."
"The way to solve this problem lies in how to communicate what kind of games [they CAN play]."
Satoru Iwata, Nintendo President. Only slightly paraphrased.