What makes you think a 45nm Fab will cost *AMD* $4.5bn ? Fab36 is going to do 45nm and that only cost AMD a billion or so. With an asp still under $100 there is plenty of scope for 30% marketshare once capacity is there.
Fab 36 can easily do 45nm... The issue with 45nm is IBM has not promised it until 2009, which is a bit late... 65nm INTC leads by 6 to 12 mo. 45nm INTC leads by 12 to 24 mo. --Alan