I dont know how much it costs to make specialized hardware. But i think there was a missed oportunity in cartridge based handhelds. There were a couple of games for GB,GBA and DS that had gimmicky controls that came from the cartridge. As the gyroscope for Yoshi Tipsy Turvy, Wario Ware Twisted and Kirby Tilt n Tumble. Another one was Guitar Hero for the DS and i think there was one with a light sensor for the GB? Thi…
It came with a solar sensor on the cartridge that required the gamer to go outside to charge their solar gun in order to kill vampires. Very cool, but it grew annoying fast.