There is no exact science but with Ni laterite ore, the end user...

There is no exact science but with Ni laterite ore, the end user pays a percentage of the dry weight (laterites usually contain 30-35% water). The percentage tends to vary with two key inputs- the firmness of the market (that is, how much can the buyer screw you) and the Ni grade. The percentage increases with grade.
The spot price I quoted earlier for Indonesian 0.9-1.1% Ni was as of last Friday, so assuming a moisture content of 30% they are only paying 10% of the contained Ni value ($26000/tonne Ni times 70% times 10% equals $18 per tonne of dry 1% Ni ore). Trust this is of some help.