what's driving down SO4 ?, page-7

As you suggest the bigger picture is probably at play.
The Aussie dollar is strong and whilst there has been some rise in SOP prices they are still below the level some of these companies used in their studies.
It will be interesting to see if commissioning and actual production at SO4 and KLL does anything to excite investors and lift the sector. I think the initial sales figures are likely to fall short of feasibility predictions.