Z+IBG charting, page-35

Duguld costs 68-78c a pound. Citronen should be at the lower end of that (currently 71c before taking into account lower oil prices.).
1.2 Billion development cost for Duguld vs 430 million for Citronen.
170000 tpa zinc 25 years for Duguld. Only the high grade zone for Citronen 185000 tpa zinc for 14 years (much longer for lower grade resource).
On these numbers funding shouldn't be hard to find for IBG. Everything comes down to a favourable tax/royalties structure (#1 risk imo) and mining licence which could happen anytime in the next few months.
IBG current market cap 20 million AUD. NPV of Citronen pre tax 600 million USD.