if FC is currently paying $1.50/GH
where does this number come from? I've seen you mention it a few times, but I don't think I've ever seen where you got it. Did FC publish that?
He never published it. It's an estimate based on FC's old balance sheet, where he had listed the total cost of making all the hardware. Then I figured about how many TH he'd produced based on his total sale profits divided by price/TH, plus the known farm size (~50 TH).
The USB sticks were a complicating factor. Obviously it is a rough estimate but it is better than nothing.