I am "under the impression" that after you have designed a "mask set" of a microchip, you will have to pay millions to have it manufactured. If the mask set contains errors, you have to fix them and pay millions, again as starting costs, to have this one manufactured. Then when you start to mass produce, the cost per chip starts to decrease.
Today's FPGA:s are a more affordable choice, as is proven by MiniMig. And J. Schoenfeld's cloning of Amiga chips, not only as a one chip implementation, but more or less each chip emulated by it's own fpga.
