I would like to build the whole thing for less than $15 (qty 100). I looked at the MSC1210 but at $12 in 1000s off, it's a bit to pricey. Considering that you will need a 4 layer PCB and things like RS232, Linear regulator, DAC, etc cost add up quickly.

Cost of the micro should be in the $6 range.

Looking at the Dominos, Stamps, Basic Tigers (these seem very good but still pricey) I just thought one can build something with all the features for much less.