Depends if a company hedges its metals or not. Also depends on whether cash costs/oz are going up, whether there are enough financial resources in a company to get the metals out of the ground, too many factors.

In your logic the share price should stand still if gold went sideways - that logic doesn't apply either. I held Yamana for many years and sold some three years ago. It was a success story up to a certain point. In 2008, gold went down 10-20% max, Yamana went down 75%. Cash costs are still low and fundamentals positive but Yamana is a predator now and those come at a price. I'd rather buy the prey than the predator.