maybe I am not explaining it correctlyyou wrote the...

maybe I am not explaining it correctly
you wrote the following
"1300 x 400 x 30 x 2.5 = 39Mt

@55% fe = 21.45Mt @ $10 EV/tn = $214m EV"

The total tonnage of ore you have listed as 39Mt
then you discounted to show the pure Fe% as 21.45Mt

However while ore is sold FOB or COF on units of Fe per ton (there are 100 units in a ton), similar to your final calculation shows above 21.45 million * 100 units * price per unit.
But I have not seen resources/reserves compared on a units of Fe basis
Reserves/resources are normally calculated on a total amount of ore in this case the 39Mt you calculated and then compared takeing into account impurities and Fe % compared to Brockman type ore or another designated
benchmark ore type IMHO.