economics of extraction

Im a bit of a newbie to heavy mins so bear with me.

Averaging all their data (a bit crude) gives $1.6bn of value in 260mt of material, or $6 of value per tonne of material.

Not sure how the grade of 2.4mt compares to others, but the % of Leucoxene and Zircon (the high value stuff) looks pretty low. Most of the deposit is low-value ilmenite.

I dont know a hellva lot about dredging either, except that the cost must be sensitive to fuel costs.

Any thoughts? I am aware more data on the way but this does not seem that great to me. Happy for people to show what I'm missing.