Get a mining calculator on the same day the ship is ship-able. Calculate the return the chip generates (at 100 GHash/s) per month with the NEXT (estimated) difficulty. Multiply that number by 8 (this is when it should break even). And there you have it ... the price of one chip.

Right now the cost would be:
Next est. Difficulty: 1.52542370411e+11
with 100 GH/s
per month: 0.01003473 BTC
multiplied by 8: 0.08027784 BTC total cost per chip (in a functioning miner ... PSU, housing etc. included) which currently results in 30.45 USD

Enjoy!