There are no legitimate deals on new Vaporfly Next % to be found (other than someone using it as a loss leader, I suppose). The price is $250. If you find it for less it is because it is different than a legitimate vendor's product.
Not so sure about that. Eastbay has them quite a bit for 25% and even 30% off at times. They were $187 for Black Friday I believe. Dick's Sporting Goods also has them on sale every once in a while. It's to the point where I would never pay $250 for them because deals are pretty easy to come by. I think the regular Vaporfly 4% were as low as $125 on Eastbay this week, although most of the common sizes are gone.
If you're lucky, you can get 15% off codes for Running Warehouse as well. Nike .com even has them on sale at times. There were about 15 pairs of the pink Next% at the Nike Outlet store near me for $175 last weekend. Lots of options.
I have purchased fake shoes on ebay by accident (Nike Flyknit Racers) and eBay backed me up and refunded my purchase immediately. So there is recourse in the event you get a bad deal. That said, it's a hassle to order shoes, get fake ones, then have to go through the process of a refund and have to ultimately buy new ones somewhere else.