Towards a RXL Valuation?

DYOR - I am not an expert or have any experience in mining.
Just a brief comparison with some figures from the Sirius Nova Projections:

SIR BMO Conference Presentation
Page 7:
DFS forecast C1 cash cost of US$1.50/lb* •
DFS forecast all-in sustaining cash cost of US$2.09/lb*
Page 10:
C1 cost* US$1.50/lb, A$1.66/lb

* Based on 100% payability

RXL Company Presentation 17/2/2015
Page 12
Operating Cost (C1) A$207/t  (Two mines: Camelwood/Musket)

Assuming an approx 2,200 lbs/t
This gives a Operating Cost (C1) of less than A$0.10/lb for RXL (approx 10 cents)

Of course, Sirius Nova is larger and far more advanced (mining started I think).

So have I made a mistake in my calculations or assumptions?
Can anyone explain the big difference in C1 costs?
DYOR

Just for interest this article:
http://www.macrobusiness.com.au/2014/03/iron-ore-prices-and-mining-profits/
comments on C1 cost estimates