Excluding the impact of foreign currency fluctuations and deflation in gasoline prices, Costco's comps for the month under review rose 1%. Costco Wholesale CorporationCOST registered an increase of 1% in comparable-store sales (comps) for the month of September (the five weeks ended Oct 2, 2016) following flat comps in August, a 2% decline in July and again flat comps in June. Costco posted flat comps for the quarter.