Should I buy this Plycraft Mr. Chair for $200?  

No.
No. No you shouldn't. Nope.

if you really want a knock off...
if you really want a knock off 670 / 671, they're all around for a few hundred dollars...and in better shape.
That's just my opinion.

I almost
bought one a week ago for $60 in better shape, but was simply going to flip it. Already have a plycraft eames knock off that I prefer. I go Faux.

Personally,
As far as Eames lounge knockoffs go, I like that button-less Mr. Chair you're looking at better than the more straight-forward copies.
That said, even if you like that design, you'll see them from time to time, in much better condition, for around $300.

Are these really considered...
Are these really considered 670/671 knock-offs?
I've always considered the various plycraft chairs that resemble the original eames lounge to be interesting designs in their own right, despite being obviously inspired by the 670/671. I've also found that some of the plycraft chairs are actually more comfortable than the original eames version.
One of my favorite plycraft chairs is this one: http://vintagemodssf.com/post/4081749537/george-mulhauser-pycraft-lounge...
Unfortunately, I've never actually been able to find one in my area 🙁
I've seen plenty of really cheap looking vintage knock-offs, including the Selig version that look like direct copies as opposed to the Plycraft chairs.

Plycraft
This Mr. Chair, I don't see as a direct knock-off.. But there are Plycraft chairs that I'd definitely say are Eames copies.
As far as a favorite, my favorite Plycraft design is this one, which I have a pair of. Mulhauser Mrs. chair body, but with Cherner legs.. I've always assumed its a "lawsuit chair," due to Goldman's many misdealings... But I can't find much about it.

I'm sorry
but these questions are starting to make me nuts.
Should you buy it? How should I know? Do you need a lounge chair and ottoman? If you do, and you like the design, sure. Is it a good price? Yes.
Waffle says that they passed on one for $60, and I am sure there is someone else out there who bought one at a garage sale for $10 in mint condition. But there are many people who paid much more. Where can you buy a decent quality lounge chair an ottoman with any degree of design or history for $200? If I came across that chair, I would clean it up and sell it more than $200. But that is what I do for a living.
I don't understand this decision by consensus. If I took a poll for everything I bought (either for myself or for resale) I would loose my mind. Sometimes you just need to look at something, assess the value to you (price and aesthetics) and decide if you can use it and like it. At $200 it's a modest investment. If you find a chair you like better down the road, I would think you could easily sell this one for close to the same money (or probably even more).
And remember, it's always better to regret the chair you did buy than the chair you did not.

Umm..
I was under the impression that no one who frequents this forum sells anything.. at least not EVER for more than they paid for it... 😉

let me clarify
I FAILED to buy one. I was sick and couldn't make the commute to pick it up. I would have bought it! And maybe kept it...I rather like that ver. of the Mr. Chair. And I really do have a brown ver. of the eames knock off that I quite like!

Hello! I wanted to join in on this older post because I have a plycraft chair, just like the green one posted, but off-white. I got it for free and it is just in my garage because i have nowhere to put it. I didn't even know that it was a chair that collectors appreciate, I simply liked the look of it. The vinyl on it has gotten discolored over the years, and I thought about recovering, but realize that my not be a good idea. I can't find much information online about the chair, so I wanted to reach out.