Take that link (Steam Deck page on the Steam store), scroll down a little bit. Red banner says “On Sale Through December 4th.” To the right are the 64GB LCD Deck, which is out of stock, and the 512GB LCD Deck, which is still discounted to $336.75 and has a Buy Now button under it. I was, seconds ago, able to add it to my Steam cart and remove it.
If you’re in the US, I’m not sure you’re looking in the correct place?
Take that link (Steam Deck page on the Steam store), scroll down a little bit. Red banner says “On Sale Through December 4th.” To the right are the 64GB LCD Deck, which is out of stock, and the 512GB LCD Deck, which is still discounted to $336.75 and has a Buy Now button under it. I was, seconds ago, able to add it to my Steam cart and remove it.