reality check on costs

I was talking to mechanic who worked up at Lihir Island last year. Wondering why the price is so low and the mines not making money? Picture this, Lihir Island is a 2 1/4 hour flight from Port Moresby and about 3.5 hrs from Cairns on the daily plane that NCM charter from Cairns.

Currently the aussie expats there are doing either a 9 days on, 5 days off roster or a 21 days on 14 days off roster. This means that for every expat position, there are 2 expats so that there is coverage. Can these guys and girls not be away from mommy for more than 21 days?

What is the cost of this?