I don't know much of FRS, but when having a quick look at their IP March 2010 report (P.2 Resources), they only have 277Mt DSO and with a lower grade than SDL. The killer here for FRS is their DSO operating costs which is $32 to $36 per tonne and this is in Aussie dollar (see a little note on bottom of P14 - FRS IP report).
Compared with SDL, where estimated Production Cost (DSO) = US$19.65/t, and using the same parity in FRS report with Exchange Rate A$0.75 to US$, we have for SDL an estimated Production Cost (DSO) around AUD$14.75 per tonne:
So FRS estimated DSO operating costs is more than double compare to the SDL one.
P13 & P14 - FRS Scoping Study Project Payback Period: 6 to 8 years Project IRR: 21 - 30 per cent Product Grade: 58.5% Fe Operating Costs: A$32 to A$36 per tonne
FRS DSO: - 191Mt of High Grade Resource (+55% Fe) - 85Mt of Medium Grade Resources (between 50-55% Fe)
SDL DSO: - 415Mt at 62% Fe - Estimated DSO Operating Costs = US$19.65/t (or A$14.75/t)
It would be interesting if Westcott could bring some further analysis on this.