My understanding is that a 40nm fab is only economically viable if it's spent the first several years of its life producing high margin chips.
In other words; the life cycle of a 40nm fab is:
1997: start building fab
2000: fab goes online and starts producing CPUs
2006: fab upgraded
2012: fab switches from CPUs to video and memory controller chip sets
2018: fab switches to USB controllers and embedded chips
2019: fab offline for 2 months because an antiquated but critical part is broken and is only brought back online because another similarly old fab went offline and sold off their parts
2020: fab shut off because of covid
2021: fab found to be a write-off because too many things broke while fab was offline.
So if you skip straight past the profitable phase, you end up spending billions of dollars to make a fab that makes $0.30 parts, and it'll never be profitable unless those parts are $10 each, which in turn makes the product they're in unprofitable.
In other words; the life cycle of a 40nm fab is:
So if you skip straight past the profitable phase, you end up spending billions of dollars to make a fab that makes $0.30 parts, and it'll never be profitable unless those parts are $10 each, which in turn makes the product they're in unprofitable.