Bandi - costsI have long used 12USD/ton as a break line for costs involved in open pit operations. This means that if the value of the minerals in the ground is less than $12, it will never fly. Above $12 it's possible. The closer to $12 it's less likely. If it's much greater than $12 more likely.
I use $25USD/ton for underground operations.
There are a whole number of other considerations that influence that and generally add costs. But these are valid breakpoints that represent the lowest cost of mining.
Total cost for feasibility - is really a tough call. $250-500 million is a guess. Al Hariqah will take less than Suwar.
Al Hariqah could get by on less upfront by concentrating on one area and starting a smaller operation. But that would also negatively impact total ROR for the operation.
Last case study I got involved with concerned a small underground gold mine in Washington State. They put 250 million into advancing the mine from exploration to production. Unfortunately, they spent 500 million trying to meet all the permitting hurdles. The mine was finally opened and has operated intermittantly since. No way will they ever make payback. US environmental regulations, NIMBYs, and tree huggers made sure that all the mining company ended up with was a big shaft.