Here in the UK a used 5D2 in good condition sells for about £550-650, depending on if it also has all the accessories, original box, kept out of smoke, etc. A used 6D(mkI) is about £850-950, so you can pay quite a bit more for what is essentially a slightly better center focus point.
For that ~£600 price point, the 5D2 is a good camera. That puts it around the same price as a 200D/SL2, and I'm sure most people will agree that for most stills work and for any low-light, manual focus video, the 5D2 is a better buy than the 200D/SL2. At that price point, at workshops/talks I regularly recommend any beginner save for a good condition used 5D2, or make that their first upgrade if they need to start off with something even cheaper (often something like a used 60D) first. I also often recommenced it as a solid backup camera for pros, and I myself have a 5D2 which fills that role, as well as being the 'disposable' SLR for when I need to take a camera somewhere where my little Fuji's battery won't last, but I don't want to risk the value and insurance of my Phase, a 1D, or newer 5D; it's better for a £600 5D2 to be broken, lost, or stolen, than a £5000 1DX2.
Does the 5D2 still have a use in 2018? Absolutely. At the full Canon refurb price? No. Is it worthwhile as a main camera to people who can comfortably afford a 5D3, 6D2, or Sony α[whatever]? No. But for tighter budgets, for beginners, or as a backup, yes, it still works very well. Newer sensors may be better, newer processors may be faster, newer focus systems may be more advanced, but that doesn't mean the 5D2 is any worse than it was originally. It's been a workhorse for years for good reason; the stills quality holds up, the video quality holds up as long as you don't need advanced frame rates or more than 1080p, the focus is still in the 'good enough' camp (though one more generation and the entry-level SLRs should finally overtake it), etc.
Don't pay Canon's overblown refurb price, but get a good price on one and they're still good cameras.
