Investors have had to take sales growth metrics with a grain of salt in recent quarters. Many consumer-facing businesses are reporting higher revenue simply due to price increases, which are offsetting lower sales volumes. McDonald's (MCD -0.53%) endured declining customer traffic this past quarter, for example, yet its comparable-store sales were up 4% in the core U.S. market.Domino's Pizza (DPZ -0.25%) is growing through other, more impressive means. The pizza delivery leader recently announced a return t ...