Costco's 9.8% Same-Store Sales Growth in Q3 2026 Shows Why Investors Love the Retail Stock So Much

Costco reported fiscal Q3 revenue of $70.5 billion, up 11.6% year over year, with diluted EPS rising 15.2% and same-store sales increasing 9.8% (6.6% excluding gas and FX). The article highlights Costco’s resilient business model and strong consumer demand despite inflation, macro uncertainty, and higher interest rates. While fundamentals remain solid, the stock already trades at a premium 48x P/E, which may limit near-term upside.

Analysis

COST is still behaving less like a retailer and more like a quasi-defensive utility with embedded consumer optionality: when households feel pressure, they trade down into value and basket consolidation, which preserves traffic and can actually widen Costco’s relative share of wallet. The second-order implication is that weaker macro is not the primary threat to earnings; the bigger risk is that the market continues to capitalize this resilience as if it were permanently scarce, keeping the multiple detached from any reasonable cyclicality adjustment.

The key competitive dynamic is that Costco’s scale advantages compound in a soft-demand environment: vendors are more willing to defend shelf space, members are less likely to churn, and management has room to lean into traffic-driving promotions without visibly impairing economics. That creates pressure on mid-tier mass merchants and discretionary retailers that rely on less sticky customers and thinner brand trust. If inflation stays sticky but slows enough to keep nominal ticket growth elevated, COST can still report strong comps while rivals get squeezed on margin mix and inventory turns.

The contrarian setup is valuation, not fundamentals. The consensus is treating Costco’s stability as if it deserves an evergreen premium, but the stock becomes more fragile as rates stay higher for longer because the downside is multiple compression, not earnings collapse. Over the next 3-6 months, the catalyst to watch is any deceleration in comp growth once gas and FX normalize; that would challenge the narrative while leaving the business still healthy, which is the exact scenario where the stock can underperform despite good operating results.

Key Decisions for Investors

• Avoid initiating fresh longs in COST at current levels unless on a pullback of 8-12%; upside from here looks limited versus the risk of 15-20% multiple compression if comps normalize over the next 2-3 quarters.
• Consider a pair trade: long COST / short a weaker discretionary or mid-tier retailer over 1-2 quarters if you want defensive retail exposure, but size the short leg carefully because COST’s quality premium can persist longer than expected.
• For tactical expression, sell out-of-the-money COST calls 2-4 months out against a core position; the thesis is that implied strength is already expensive and upside is likely capped unless same-store sales reaccelerate.
• Watch for a catalyst-driven reversal in the next earnings cycle: if ex-gas comps fall below the mid-single digits, expect the market to de-rate the stock quickly even without any fundamental deterioration.