One would think the price would drop. But, as I mentioned in the original post, there was really no change.
I found a couple of places (via pcbshopper) which would quote the full size. As I said, $300-$400 for 3 boards. Chopping the board up would still require about $300 ($100x3) for the full circuit.
$30 or so of perfboard for the key matrix might be doable. The main circuit would be pretty cheap at that point.
I had another crazy thought. I haven't wire wrapped in 30 years or so, but that might be a solution as well. The issue is that the boards need to be big for the switches, but the component density is very low. Throughhold parts would be easy. There would still be enough space between switches for a small battleship.