He is saying that if they had done due diligence, if they had honestly extrapolated the costs of previous experiments using the demonstrated empirical scaling laws, they'd have gotten costs closer to what ITER has ended up costing. They either knew or should have know the initial cost claims were dishonest.

The US opted out of ITER in 1999 and returned in 2003. The cost of constructing ITER was estimated at €5B in 2006. How could the earlier US pullout excuse the inaccuracy of that estimate? Your narrative there makes no sense.