Really, if you compare the price-per-button, these new controllers aren't too pricey at all. http://www.nintendoworldreport.com/newsArt.cfm?artid=23240 Mad Catz has announced the pricing for the new instruments for Rock Band 3.
The most significant addition to the Rock Band gameplay is the new wireless keyboard controller, which features a 25-key wireless keyboard which can be laid flat on a table or held up with a strap while playing. The keyboard peripheral can also be used to play the guitar tracks. It will be priced at $79.99 if purchased separately, or $129.99 bundled with the game.
The Rock Band 3 drumset features a new cymbal kit, the PRO-Cymbals Expansion Kit, which is made to both reduce the sound made when hitting the cymbal and also increase responsiveness. The cymbal kit will be released separately at $39.99, but will also be bundled with the drumset controller.
Perhaps the most impressive new controller is the 120-button Fender Mustang PRO-Guitar, retailing at $150. The guitar is designed after the Fender Mustang, and contains six actual guitar strings and a 17-fret neck with six buttons on each fret. This guitar is meant for the Rock Band 3 Pro mode, which is designed to teach you how to play an actual instrument. The guitar also functions as a MIDI device, like the keyboard.
Finally, at $39.99 is the MIDI PRO-Adapter, which allows players to take any of their MIDI instruments and use them as Rock Band 3 controllers. The MIDI Pro adapter also has a D-pad and controller face buttons so that it can be easily used to navigate game menus.
Rock Band 3 launches this fall for all console platforms.