I posted a table of random numbers last week I think which might help. A couple of things:
1. A$500m in the bank puts a floor of about 47c;
2. I think break even is around US$101/t, including pellet premium
3. I haven't seen any published price estimates for any period ... 1 month, 1 year, 1 decade, 1 lifetime. And to be honest, much of the analysis and forecasts I've seen don't seem to be able to distinguish between 58%,62%,65% or even basic bloody dirt!
4. I was here when IO was trading at US$63/t I recall. It hurt! I suggest that this would be the absolute floor Fe 62% fines. I think a few IO miners went bad and buyers are smart enough to know that there is no point sending suppliers broke.
5. GRR I think is a fairly cost competitive miner. And will stay that way if they can keep a lid on energy costs and maintain access to reasonable quality material. Regardless, I think that there cost structures are informative as to what might be referenced looking ahead. On this basis, I think that a cost around US110 / t is a fair basis for long term market pricing.
5. The pellet premium ought to look something like the cost of pelletising ... again, GRR are about as efficient as anyone. So I work on the basis that any long terms pellet premium will/should only move with the cost of energy.
6. Long term price pressure then will come from:
(a) people mining more difficult areas and/or lower grade resources. A few of these are strewn around Africa. Long transhipment trails; tough ground; sovereign risks, blah blah blah 
(b) steel pricing. This will always a the catalyst. If high rises could be held up by recycled paper then Fe likely to take a hit
(c) 'environmental premiums'. Fortescue is not chasing 'hydrogen based solutions' because they like the smell of it. So any comparative cost dis / advantage of alternate production methods will have an impact.
For shites and giggles if I was looking for a base valuation my sense would be to use an IO (including pellet premium) bouncing between USD130/t and USD170t escalating at around 1.5%pa (energy and to a lesser extent labour costs), an A$ somewhere nearer US75c and consistent 2.6mtpa. I suspect if you DCF'd that you'd find a pretty interesting number.
Of course, what would I know
Have a great day!
(20min delay)