Yes, mining costs changed dramatically during last 5-6 years. The reason is that gold producers saw opportunity to increase production when gold price was high and the only realistic way to do it was to bring in new ore deposits of lesser quality; the latter means higher cost.
One can also find few auxiliary reasons for higher costs: general inflation, taxes, labor demands; but the main reason is one above. Companies were willing to produce gold for “any cost” and it backfired.
A lot more shares outstanding today that 5 years ago, which is universally true for almost mid-tier gold miners. I won't be surprised if some old SEC filings from 2008 shows only 100M shares issued then.