Would like to know that, too!
Maybe this thread can be a place where people post the deals they see (or get) from Costco on the 15” MBAs.
Configurations and colors are key. Right now, through Nov 19, they're selling the 8/512 for $200 off or $1250 and all colors are available.
The product pages could be much better designed, however. The price appears on the search results list, but is hidden on the actual product page. The “Add to Cart” button is hidden! Not until you start scrolling down the page does it finally show up at the top.
The RAM amount is buried down the page rather at the top with the item blurb and SSD size! It's also unclear whether one has to be a Costco member to order... seems so as I can't add the 15” to the cart. There's a generous 90-day return policy, but it's unclear whether one is charged for a mailed return. They provide a shipping label, so one would assume so, but even that info was hard to find!
Note: The other day I that, if you buy Apple Care at the same time you buy the laptop from Costco, you get about $50 off of it — $180 rather than the usual $229 on the 15”.