Well, if you want to ramp up production with more than one manufacturing line, you might need a second mask set. For FC's volume that should be totally unnecessary, even for Gen 2.
Marginal costs shouldn't change much for the same process unless you make a new deal with the foundry.
Anyway, after actually MAKING the hardware (and doubtless encountering some speedbumps), I do wonder how accurate that estimate is.
As I understand it it's not an estimate. That comment about $10k per TH was posted in the beginning of May. ASICMiner started hashing i February. Or am I misunderstanding you?
I thought FC's estimate cited here was forward-looking to the scaled-up 200 TH production run (which has since completed) - i.e. he expected to spend less than $2M more to make that hardware.
That was just my interpretation, though. The word "final" makes me think you might be correct.