NEW YORK — As superstore pricing mysteries go, it’s not the equivalent of “The Da Vinci Code,” but there’s still something deliciously elusive about the so-called “Costco Code” that has set the tongues of shopping mavens wagging for the past several months. At least the plot line is direct enough: If you can interpret what the various sequences of digits and asterisks mean on Costco Wholesale Club price signs, you’re on your way to scoring serious bargains. Here’s how it works, according to Costco shoppers spreading the word online: If a price at Costco ends in .99, you’re paying full...