The problem is that their biggest cost is not mining+processing...

The problem is that their biggest cost is not mining+processing but rather transportation/logistics, it is the uncompressable/unshrinkable transportation costs of 125.7 US$ per tonne of graphite (Inclusive of trucking costs to the Port of Nacala (490km), storage and containerizing charges, port and custom charges) (data from the now old may 2015 feasibility study, possible these costs are now higher due to inflation).

So even if they spread their fixed costs over bigger volumes of production, they would still need to pay 125 US$per tonne of graphite produced just to transport it from the mine to the port of Nacala. These transportation costs wont shrink with higher production, they are purely variable costs. they produce 10.000 tonnes of graphite or 1 million tonnes of graphite they would still need to pay 125.7 us$ per tonne of transported graphite and there isnt much they can do about this (unless they build trains infrastructure...).

In the feasibility study they estimated 286 US$ per tonne of operating costs (excluding 3% royalities and 32% taxes) at 380.000 tpa nameplate capacity (33.3$ mining + 83.6$ processing + 43.5$ general administration + 125.7$ transportation). IMO these costs are optimistic but time will tell.