You want a servo that is precise, robust, fast, and strong.
You will not find a servo that achieves all of this for under $5. The closest you can find is Dynamixel AX-12 or Herkulex DRS-0101, each for about $45 each.
Typically, with the cheap Chinese servos, you trade off at least precision and robustness, and there is a particular choice between speed and torque -- with the same motor, twice the speed can be had at half the torque with a change in gears only, making multiple servos within the same range easy to produce.
You *can* build a biped with 12 cheap Chinese hobby servos. It will likely also be able to shuffle/walk. However, it will not be as nice, smooth, and rigid as you would hope.