$10-13/oz is the opex (or C1 cash cost) so you are calculating...

$10-13/oz is the opex (or C1 cash cost) so you are calculating operating margin, not EBIT. You would need to add in D&A, sustaining capex, admin and overheads, interest, and tax to get NPAT (not EBIT) which is what the market looks at to decide PE ratio.

Total cost will likely be somewhere north of A$20/oz which is why the SP is so heavily leveraged so silver. At the current price this project is a no-go. At A$25/oz it will be marginally profitable. But it really needs A$30+ for the leverage to kick in and drive large profit on the back of high volume.

The problem for SVL management is how to convince somebody to invest when the silver price is in no-go territory. I'm really keen to see the feasibility study, though I think it will contain a couple of rude shocks, not least the power price. IMO the basket case the state governments have made of the NEM is going to cripple a lot of marginal projects.