Gross Profit is the first margin line anyone looks at in a commodity deal. In Granel — and in a typical desk’s projections spreadsheet — it is Revenue − Purchase cost − the deal’s direct cost lines (ocean freight, inland haulage, commissions, certification, port charges, insurance).
The difference between sale and purchase price times volume, with nothing else taken off, is the trading spread. Some desks call that GP too, so when comparing margins it pays to say which of the two figures is meant.
Overhead allocated to the deal is then taken off GP to reach EBIT. Physical traders normally quote GP per unit of volume — GP per tonne — so deals of different sizes can be compared on the same footing.