Lol, I was almost going to query the $4.30 as I thought I'd seen some lower costings from sand mining comparisons but if my extensions bear any semblance to reality it only improves the outcome as you suggest.
Good example of why we need to see the numbers laid out before committing too much hard earned.
BTW, Torpedo linked to a very well written report on TUC at the NTU forum which has some relevance here for anyone that hasn't picked it up.