Costco (COST) moved higher on Friday following an earnings beat that signaled resiliency amid greater economic uncertainty. However, as Mel Casey notes, membership numbers are what matter the most to analysts to gauge guidance. A slowdown in new memberships initially sent shares to the downside, leading Mel to highlight the importance of a widening K-shaped economy. Jharonne Martis explains how Costco's report gives us a chance to look through a "fascinating window" into the state of U.S. consumer minds.