There's certainly a lot more going on than grades per tonne that...

There's certainly a lot more going on than grades per tonne that define an economic resource.

1. Other metals present in the deposit and how easy they are to extract
2. Total size of the deposit (e.g. a shallow 2Moz deposit at 3g/t would be a lot more attractive to investors than a shallow 200Koz deposit at 10g/t)
3. Access to existing infrastructure and cost of development (capex $$)
4. Whether the gold is refractory or not (how easy it is to extract)

There's obviously a lot more, but these are the things that need to be considered before anyone gets serious about even a feasibility study, let alone development.