You can buy a lot of RAM for north of $800, or you can grab the fastest memory kit in the world, Corsair's new 16GB (2x8GB) Vengeance LPX DDR4-4866. It's the only kit officially rated for DDR4-4866 on the planet right now.
I have a sneaky suspicion G.Skill will follow suit with a kit of memory that is equally as fast, or even a bit faster, but for now Corsair maintains bragging rights. The caveat, of course, is the cost—Corsair charges $984.99 on its website, while Newegg has it listed for $859.99. Either way, it's an ultra-expensive kit.
Corsair screens each memory chip for validation in its Vengeance LPX line. For this particular kit, we imagine the binning process yields relatively few chips that hit 4,866MHz, hence part of the reason why the price is so high.
The new memory kit should work in any modern platform, though it's designed specifically for third-gen Ryzen systems. Your mileage will vary if plopping this into an Intel system, or even a previous generation AMD rig.
Heck, even some X570 setups may require some finagling. Corsair is basing its speed rating on tests performed on select motherboards—Asus ROG Crosshair VIII Formula, MSI Meg X570 Godlike, and MSI Prestige X570 Creation.
At full throttle, timings on this kit check in at 18-26-26-46. Those are pretty loose, except for CL, but if you're actually able to hit 4,866MHz, it shouldn't matter much.
To keep temps under control, Corsair includes a fan attachment that sits atop the RAM and provides direct cooling. It's entirely optional, but you'll have a better shot at hitting crazy high frequencies.
This is a neat achievement for sure, but not one that offers any semblance of bang for your buck. Even among premium kits, 16GB DDR4-4800 kits can be had for a lot less (though still not cheap). For example, G.Skill's 16GB Trident Z Royal DDR4-4800 costs $439.99, and Corsair's own 16GB Vengeance LPX DDR4-4800 is $699.99.
Nevertheless, if you want the fastest RAM in the world and are willing to pay a premium for it, this DDR4-4866 kit currently holds the crown. Liquid nitrogen not required.