Intel's 5-GHz Core i7-8086K is available for order at Amazon, Newegg, and Best Buy for the un-marked-up price of $425. Yours truly had expected a markup on the limited edition of 50,000 chips (of which 8,086 are apparently already reserved for give-away purposes), but it seems that retailers are playing fair with prices so far. No telling what allocations US e-tailers got for these, so I would move fast if you want that sweet, sweet single-core speed.
In fact, I've put my money where my mouth is and secured one of these chips independently. Stay tuned as I figure out what the premium over a run-of-the-mill Core i7-8700K buys us in terms of both stock and overclocked performance, as well as that limited-edition cachet.