It's a monthly fee for the pro version but it's about a 2 yr bnreak even with just buying it at $199
If you're unfamiliar with the history, Prepar3d is an evolution (by Lockheed Martin) of the old FSX codebase - but they've updated it with multi-core support, DX11, etc. Most (but not all) FSX addons are compatible, and it gives better frames at MUCH better visual quality than FSX.
Yep, it's multithreaded. And it helps, too - things like the galaxy map are somewhat CPU-bound because of the large amount of procedural generation. (Not to say that it could be impossible to do with compute shaders helping out too, but then, ED is still in Beta 1.0 and I wouldn't expect to see really huge, complex optimisations like that at this point.)
Actually, I'd expect most new 3D engines to be prepared for heavy multithreading by now, but many new games at the moment are still based on older engines. 2015 and on, maybe not so much, when people start releasing things backed by UE4, CryENGINE (4), Source 2, FOX Engine, etc in earnest. I think the majority would target a quad-core, and might be surprised to find themselves running on a 6 or 8 core.