Wired has an interesting article about several prototypes of rather historical devices. Of much interest are the Apple 1, and the Atari 2600 although the doorbell powered Moog is pretty classy as well.
Take a look at the Atari 2600 prototype and notice that they used a MOS 6502 in it. The final version used the lower cost (and smaller) MOS (or Synertek) 6507.
When designing a product, it often is easier to use the standard full featured version of an IC for development work, and then as you refine the design, trim down to the least, and smallest components you can.
We also learn how Foxconn got its idea of low wages. Steve Jobs himself paid his sister a mere $1/board to assemble the Apple 1.
Its interesting to see how prototypes can be so vastly different from the finished product. A fact that design engineers know all to well. “I have to put all of THAT into what?”