Costco doesn't do earnings drama, and its monthly sales reports are about as close as retail gets to a metronome. The May print kept the beat — loudly. The warehouse club reported net sales of $24.01 billion for the four weeks ended May 31, up 14.5% from $20.97 billion a year earlier, according to the company's release. For the first 39 weeks of the fiscal year, net sales reached $221.19 billion, up 10.0%.

The cleaner signal sits one line down. Total comparable sales — which strip out the boost from newly opened warehouses — rose 12.5%, with U.S. comps up 13.7%, Canada up 9.2%, and other international up 9.7%, as StockTitan reported. Even allowing for fuel-price and calendar effects that can swing a single month, a double-digit comp at Costco's scale is the kind of number most of retail can only describe in the past tense.

E-commerce is no longer the asterisk

The standout was online: digitally enabled comparable sales climbed 21.1%, per the May results. Costco spent years being politely described as an e-commerce laggard — a treasure-hunt format that didn't translate to a screen. That framing is now stale. A 21% digital comp on top of a 13.7% U.S. in-warehouse comp means the channel isn't cannibalizing the box; it's adding to it. Big-and-bulky delivery, the Costco Next marketplace, and an app that finally works are quietly turning the membership base into omnichannel shoppers.

The barbell keeps getting heavier on both ends

Costco's momentum belongs to the same story Endcap has been tracking through earnings season at Dollar General and Five Below: when consumers feel squeezed, value formats win share. But Costco's version comes with a twist that should worry full-price competitors more than the dollar stores do. Its membership skews higher-income, and its U.S. renewal rates sit in the low 90s — so when Costco posts a 13.7% U.S. comp, it isn't just capturing trade-down from struggling households. It's capturing trade-over from affluent shoppers who could buy elsewhere and are choosing bulk value anyway.

That's the uncomfortable read for the rest of retail. The trade-down narrative is comforting because it implies a snap-back: when the economy loosens, shoppers return to full price. But a customer who discovers that a $65 membership reliably beats the alternative doesn't necessarily come back. Costco isn't just riding the value cycle — it's using it to make habits stick. While Lululemon trims guidance and the mid-tier department store fights for a 1.6% comp, the warehouse club just grew sales 14.5% and made it look routine. Increasingly, it is.