Yeah even in the US its somewhat regional and brand-specific. In my region, I just purchased a pack of 18 eggs for $5 USD at a typical well-known chain grocery store.
Some of these egg companies are absolutely using the bird flu as an excuse to raise prices. Right next to that 18 pack I bought was a shelf full of eggs that cost $9/dozen. No one was buying them. Just a weird situation.
Costco is culturally insane. There's a certain kind of person (cough prepper cough) that shops at Costco; these people hear one whiff of societal instability and they immediately buy ten dozen eggs, manage to eat half of them, and then throw the other half out. Its super cringe and its the reason why I cancelled my Costco membership last year.
Meanwhile you just go to a Kroger or Walmart down the street, pay nearly the same price, and they always have stock. It was the same thing with toilet paper early in the pandemic; we swing by Costco, utter madhouse, line out the door, everyone has cartfulls of toilet paper. I tell my friend "lets skip this and go try Target" -> Shelves weren't fully stocked, but they had some, no crazy crowds, we're good and the butts are clean.
Costco's prices aren't even that spectacularly great anymore, especially once you factor in the membership, and if you do a little legwork on coupon clipping (which is so easy nowadays with all the apps). E.g. the Kroger near me almost always has meat like 30% off on Fridays because, idk, its nearing the last day they can sell it or something. Stock up for the week then, way cheaper than even Costco.
I picked up a dozen for $3.99 last night at a major chain grocery store, too. They had plenty of eggs in stock and I was there around 9pm. I've seen the insanity at Costco first hand so I've stopped buying milk and eggs from there until that sorts itself out