I got a MSI Suprim Liquid X 4090 off craiglist for $1920. I would have actually preferred one of the cheaper models, but the price was basically retail + sales tax on this model and far better than scalper prices on ebay/stockx/etc. It's my first ever AIO card. The AIO seems to be only marginally better than the air cooled models, but the card is physically much smaller than the others and also exhausts all the hot air directly out of the case. It has a beautiful appearance too. I'll set it up in the next day or two and plan to just use the adapter for now. The Corsair 16-pin cable is impossible to find in stock and sells at absurd markups on ebay.
The stock tracker apps are a waste of time. I spent a few weeks with them before giving up. By the time you add it to your cart and login/password, it's already gone. I had that happen at least 5 times. If you buy from ebay/etc., ask the seller for a copy of the receipt for warranty purposes.