Most people think of Costco as a warehouse. What far fewer of those same members realize is that tucked inside their membership — accessible from the same Costco.com account they use to check the coupon book — is one of the most commercially powerful travel booking platforms available to American consumers. Costco Travel, the warehouse's dedicated vacation booking division, saves members $500 to $1,000 or more per trip through negotiated bulk pricing, bundled perks, and a mod