http://www.joystiq.com/2007/08/07/rock-band-bundles-have-wireless-guitar-on-ps3-and-wired-on-xbox/
We've been working on getting answers to what's going on with Rock Band's peripheral pricing for a long time, there are still no "official" prices to be found, but there is one anomaly regarding the wireless Xbox 360 guitar that is really starting to kick up questions. This $20 difference in the prices between the Xbox 360 wired and wireless guitar, which Joystiq first reported on back in May, has come back around in a sneaky way with the Rock Band bundles. Both Amazon and GameStop currently sell the Rock Band bundle for $199, with one key difference: The PS3 version comes with a wireless guitar and the Xbox 360 version is wired.
It seems that for some eason the wireless guitar for the 360 is 20 dollar more than that of the PS3, which is why the bundle of the same price means the PS3 gets a wireless guitar and the 360 gets a wired one.
Thanks to Blacksaber for the sig!