Shares of Chipotle Mexican Grill might look cheap at a recent $404 apiece, down from a peak of over $750 a year and a half ago. Don’t dig in yet, though. The Denver-based burrito chain is moving beyond a punishing sales decline caused by widespread 2015 outbreaks of E. coli, salmonella, and norovirus, but keeping a clean record from here while luring back lost customers could involve a long-term shift higher in sourcing and marketing costs.
Sales at longstanding stores have begun rebounding from their level a year ago,…