The attached research paper "#Gold & Precious Minerals" by Scotiabank deals with AISC (all-in sustaining cost). Generally speaking, for the senior and intermediate gold producers, a gold price of US$ 1'000 to US$ 1'100 per ounce is needed for FCF (free cash flow) breakeven.
From Scotiabank:
The industry has done well cutting costs to maintain their margins despite much lower gold prices. It's a well-known narrative that gold producers have cut spending heavily since the peaks of 2011-2012; analysis confirms that in 2016, standardized AISC margins (%) for the group have returned to levels similar to 2012 (~25-30%) when the gold price was more than $400/oz higher. "Sustaining FCF" margins (i.e., after deducting cash taxes and interest) have rebounded even further with margins now ~18% vs. 17% in 2012. Since 2012, Nemont Mining has improved their standardized AISC position the most (from seventh to third), while Yamana Gold has slipped the most (from first to seventh).