You must have been using the number from the white paper by Canon. the APS-C potential site is REALLY wrong. My estimate is that there may be only 75 sites for the 8 inch wafer for APS-C sensor. Let us assume the yield for APS-C is 75 %, then we will have 56 sensor per wafer, $5000 per wafer, that will be $90 per sensor. Assuming the yield for FF is 25% (1/3 of the yield of APS-C, being pressimistic ). then each wafer will yield 5 FF sensor. that will be $1000 per sensor. That seems about right. If wecompare the price of &D to 5D MkII, It is about $800 difference.
and that would mean $30 per APS-C sensor (166 working chips out of a $5000 wafer), which sounds pretty reasonable, and tells me this format is not going away anytime soon
My personal opinion is that the Canon white paper is used to justify the high price of the FF body. The site of the FF sensor on the wafer may be 22 to 24. That will bring the yield up to be 6 sensor per wafer. and the difference in cost will be $770 instead of $1000.We are assuming that the wafer cost is $5000. Which is extremely high for a CMOS process. What if the wafer cost is $2500, than the difference of FF sensor and APS_C snesor will only be $450 or even $370.