On an unadjusted basis, Costco recorded an even stronger 14.1% comp sales gain last month, as gasoline prices have surged over the past year and the U.S. dollar has weakened against foreign currencies. On the flip side, ancillary sales plunged last year, due to low demand for gasoline and travel, as well as temporary closures or reduced services in Costco's food courts, optical shops, and hearing aid departments. While year-over-year comparisons will become a bit tougher over the next few months, Costco's strong June sales performance should give investors confidence that comps will remain positive for the foreseeable future.