COST · Costco Wholesale Corporation

The thesis

Costco Wholesale shares look more likely to track the S&P 500 than beat it over the next three months. Underlying sales growth slowed for three straight months through August, and the shares still trade at about 40 times forward earnings. September sales, due after the close on 7 October 2026, show whether that slowdown has stopped.

The fiscal fourth quarter, reported on 24 September 2026, was strong. The monthly trend is weaker. Comparable sales adjusted for gasoline and currency rose 8% in May, 7% in June, 6.6% in July and 5.4% in August, according to Motley Fool on 4 October 2026.

The narrative is maturing: the compounding-retailer story is widely known, and the fourth-quarter beat brought four target cuts between 25 September 2026 and 28 September 2026 rather than upgrades. The bar for September is set. Telsey Advisory Group expects adjusted comparable sales of 6.5% against 6.0% a year earlier, and total comparable sales of 10.1% (Investing.com, 5 October 2026). The shares rose into the report, closing at $935.68 on 6 October 2026.

Bullish and bearish views on Costco Wholesale Corporation

The bull case on Costco Wholesale Corporation (COST), in brief: Sales growth is strong at scale. The bear case: Underlying growth is decelerating.

Bull case

• Sales growth is strong at scale. Fiscal 2026 net sales rose 10.1% to $297.2 billion. Fourth-quarter adjusted comparable sales rose 6.7%, with the US at 7.2% (company release, 24 September 2026).
• September has calendar help. Telsey (5 October 2026) credits the Labor Day shift with about 0.5 percentage point of September growth. Motley Fool (4 October 2026) estimates the same shift took about 0.75 point off August's 5.4%.
• Traffic and ticket are both rising. Telsey forecasts September traffic up 4.0% and average ticket up 6.1%, against 2.1% and 3.5% a year earlier (Investing.com, 5 October 2026).
• Membership income keeps compounding. Membership fee income rose 7.3% to $1.85 billion in the fourth quarter. The US and Canada renewal rate rose 0.1 percentage point to 92.3%, and paid members rose 3.8% to 84.1 million (24 September 2026 earnings call).
• Most covering firms still see upside. Telsey reiterated Outperform with a $1,135 target on 5 October 2026. Deutsche Bank kept Buy at $1,079 and Argus kept Buy at $1,230 on 28 September 2026 (Benzinga).

Bear case

• Underlying growth is decelerating. Adjusted comparable sales fell from 8% in May to 5.4% in August, three straight monthly declines (Motley Fool, 4 October 2026).
• Reported sales flatter demand. Telsey (5 October 2026) estimates gas prices up about 35% add about 3.6 percentage points to September total comparable sales. That explains most of the gap between its 10.1% and 6.5% forecasts.
• Canada and international face hard comparisons. Telsey forecasts September adjusted growth of 3.0% in Canada against 9.3% a year earlier, and 5.0% internationally against 7.5%.

• Cost inflation is pressing margins. Gross margin fell 0.11 percentage point to 11.02% in the fourth quarter. A LIFO (last-in, first-out) inventory charge of $152 million, against $43 million a year earlier, was tied to memory-chip, fuel and resin costs (Benzinga, 25 September 2026).
• Valuation leaves little room. Yahoo Finance, citing TIKR, put the shares at 40.5 times forward earnings on 29 September 2026. Roth Capital repeated Sell with a $781 target on 25 September 2026, and Truist cut its Hold target to $955 the same day.

Price setup

The shares closed at $935.68 on 6 October 2026, up from $923.52 on 5 October 2026. That close sits 14.4% below the 52-week high of $1,092.58 and 2.7% above the level of three months earlier, on adjusted daily closes. The 52-week low is $844, as cited by Yahoo Finance on 29 September 2026.

The 14-day relative strength index (RSI) stood at 74.1 on 6 October 2026, above the 70 level commonly read as overbought. That run-up came in the sessions before a scheduled sales release, so part of a September rebound is already reflected in the price. A September figure near Telsey's 6.5% would meet expectations without beating them.

Catalysts, next 30 days

• ~4 November 2026, est.: October sales. A second month confirms or breaks the September reading and shows how much fuel inflation lifts reported sales.
• ~10 December 2026, est.: Fiscal first-quarter 2027 results. This is the first quarter without the tariff-refund benefit, so it shows whether margins and EPS growth hold on their own.

Elapsed catalysts

• 7 October 2026, after the close: September sales for the five weeks ending 4 October 2026, the first monthly report of fiscal 2027. The figure to watch is adjusted comparable sales against August's 5.4% and Telsey's 6.5%. (passed 5d ago)

What would change the view

The growth case breaks if adjusted comparable sales in the September or October report come in below August's 5.4%, even with the Labor Day shift helping September. Canada at or below Telsey's 3.0% forecast would point the same way. A LIFO charge above $152 million or another gross-margin decline at the fiscal first-quarter 2027 report would show cost inflation is still winning.

The view would turn more constructive if adjusted comparable sales reach 6.5% or more in both September and October, with US traffic growth near Telsey's 4.0%. That would show the May-to-August slowdown was largely calendar and comparison effects. On price, a daily close below $844, the 52-week low, would show the market rejecting the case regardless of monthly sales.

What it trades with

Costco trades with large defensive retailers such as Walmart and BJ's Wholesale, and fuel prices move its reported sales more than its underlying demand. It is also a Nasdaq 100 member. Benzinga reported on 5 October 2026 that the Nasdaq 100 traded at records while 55 of its 101 stocks sat below their 50-day averages, so index gains have come from a narrow group of mostly technology names. Costco's relative performance depends on whether that leadership broadens toward defensive consumer names.