MANDURAH, Australia—One of the fastest-growing costs in the global mining industry are workers like James Dinnison: the 25-year-old high-school dropout from Western Australia makes $200,000 a year running drills in underground mines to extract gold and other minerals.

The heavily tattooed Mr. Dinnison, who started in the mines seven years ago earning $100,000, owns a sky-blue 2009 Chevy Ute, which cost $55,000 before a $16,000 engine enhancement, and a $44,000 custom motorcycle. The price tag on his chihuahua, Dexter, which...