In the latest reported period of Q3'26, Costco (COST) demonstrated diverging margin performance, with a Net Profit Margin of 3.11% and an Operating Margin of 3.99%. However, the Gross Margin experienced a significant outlier, dropping to -25.06% during this period, while other profitability metrics remained relatively stable. The overall trend from Q4'23 to Q2'26 shows consistent stability across all margin types, with Gross Margin generally fluctuating within a tight range of 12.3% to 13.1%. Operating and Net Profit Margins maintained steady trajectories, peaking near 4.00% and 3.11% respectively by Q3'26. Despite the sudden volatility in Gross Margin in the final quarter, the underlying operational efficiency reflected in the Operating and Net Profit Margins suggests a resilient core business model throughout the period.