Should I buy McCobb desk/chair for $700?  

This one?
The one with the splayed and tapered legs?
To answer your question... yes. $700 is a very fair price for a desk and chair of this quality of design and manufacture if it is in good condition. I just bought one recently in excellent condition for nearly the same price with the intention of reselling it.
I do not agree that the prices being asked on line are outrageous. I don't follow eBay, but on 1st Dibs, that desk ranges between $1500 and $3700. Of course, everyone knows that nearly every dealer is willing to discount their prices if asked nicely. You ask what they are going for, but it seems like you answered your own question... more than $700.
Where can you get a new product of that quality for less? I think that if you have a use for a desk and chair, you like that design and it meets your needs, space, and aesthetic, you should certainly buy it.

Yes, that's the one
It is in good condition. Thanks so much for your reply! You saved me the agony of ambivalence! I'll scoop the set up today.
Good to know the prices on 1st Dibs are somewhat realistic for market value.

first of all
you should know that PEGBOARD is a seller on 1stdibs. That does not mean that his/her advice is not good. But just know that $700 is not a steal, it is if anything, the price for which it would possibly fetch on Ebay if in great condition. Reviewing completed Ebay sales (where the item has actually sold) will provide you with "realistic" prices.
That being said, if you are looking for a nice looking desk and chair then you should go for it as they will not pop up locally too often and purchasing something like this on ebay would be a pain in the a%$.

Hi
Shipping cost and the risk of purchasing remotely are also factors.
If the item is local and you can see it in person, that may be well worth any nominal overage in price.

Fair to High
A desk without the chair sold in May for $255 on eBay. A chair will set you back $50-200. Another desk with the chair sold for $400. The first in Denver and the second in Michigan. I watch McCobb very closely on ebay. While they don't pop up locally very often, I think it is worth waiting for the right price. 1stdibs sells to a certain clientele that doesn't like to with waiting. I would certainly love to own one of these desks if I got it at the right price. However, I must say, I would have to make room for it. Much like most peoples lifestyles these days, desk like these are not conducive to the way we live.

I don't want
to steer the buyer in the wrong direction. There is a benefit to actually being able to see what you are purchasing as opposed to purchasing this on Ebay plus the fact that I can picture a leg breaking during shipping. I have received my fair share of Ebay items damaged secondary to usually a combination of poor packaging and manhandling of the item by UPS etc.. I know we have all at some point in time received an item that is chipped, stained etc and this was not disclosed in the listing. Imagine having to send this back or having to try and get a partial refund.
$700 as Pegboard stated would be pretty good if it is in nice condition knowing that your get to examine it and not shell out probably $200 for shipping. I do however think that Pegboards statement that prices being asked online (referring to 1st dibs I presume) are NOT outrageous is a bit out there and unfair to present to a new member of the forum who may or may not know better.

You're right.
You're right about the importance of being able to buy items in person. Both of those desks that I mentioned were sold as "local pickup only".

Sorry
... if I was not clear with my statements.
I do understand that there is a wide range of people and opinions regarding budget and value. I did say that I do not follow prices on eBay. When I do look on there, it seems very bizarre to me. I see sellers asking prices the same or even in excess of those I see on 1st Dibs and many of those sellers do not have any of the overhead that those of us selling on 1st Dibs or in any retail context incur. I do not think that someone selling out of their basement or garage with little or no history or reputation at stake should reasonably expect to realize similar prices as a dealer with rent, utilities, staff, advertising, a long history of experience and a good reputation who will stand behind their merchandise.
I did not suggest that the desk and chair was a "steal". I said it was a good price. One I would be happy to pay if I wanted the same item. And as I noted, I paid essentially the same price for a very fine example with the expectation of selling it for more. I did have to invest in the item (cost basis), and I will have to store in our showroom or studio/ warehouse it until it sells (rent). It will cost me if I list it on 1st Dibs (advertising). I will likely have to discount it, and if it sells on 1st Dibs I will be charged a commission. I will have to present it with several nice photographs, not just a quick cell phone pic in my garage, describe it throughly and give a clear, candid condition report. I will also have to facilitate safe reliable shipping. I will not be wrapping it in bubble wrap and dropping it off at the Grayhound station where it can be destroyed. To me, those things all have value and add to the cost of me offering it for sale. So when I say that $700 is a good price for a nice piece when others are selling for double or more, I guess I am looking at it from that perspective.
It is true that many of the people who buy on 1st Dibs are designers and collectors who do not want to wait months or years until they find an item at an auction, on eBay or in the Goodwill. They are looking for something specific, something special, something to fill a need, and they are willing to pay a fair price for that item. That is not to say there aren't many dealers on 1st Dibs who I think are VERY aggressive with their prices. But we have always tried to be realistic and fair with our prices and tried to offer items at a range of price points in an effort to appeal to a broad range of buyers.

cont.
I know there are those who think that collectible high design furniture and design should be bought very inexpensively, and I began collecting many many years ago in thrift stores and at flea markets so I understand the thrill of the hunt, and the exhilaration of a great score. But I have also come to appreciate value in quality and design. If you buy things that are well made and well designed (and yes vintage or collectible) they will hold up visually and physically offering years of service and enjoyment rather than ending up on the curb or in the landfill when they break or you tire of them. Frequently they will hold their value, sometimes they even increase, which is nice. Regardless of any collectible cache or investment value I often look at vintage pieces and think, "what would a comparable item cost if you bought it new". Do you think you could buy a handsome solid wood desk and chair of the same quality today for less than $700?
I am currently in the market for a Nelson steelframe desk for my son's room and while I buy things all the time at what I consider wholesale (from auctions, estates, other dealers, etc). I would not hesitate to buy one from a dealer on 1st Dibs if I felt the price was fair. I will not spend $2000 or $3000, but I would be happy to pay $800- $900 for a nice one that met my needs. And seeing that some dealers price them around $1200 on 1st Dibs I may well buy one there if I find one I like and they extend a discount to me.
I don't begrudge the people who provide me with goods and services a fair profit so they can make a living. I know most people understand that the grocer, the plumber, the tailor and the school teacher all need to pay their bills and feed their chidren, and they are OK with them earning a living. I have never understood why some people resent art and antique dealers from selling something for more than they bought it.
I will concede that you may well be able to buy one for less elsewhere, but if as you say it is in good condition and you do not have to pay shipping or incur other expenses, I think based on the quality of the design and construction it is a good value.

Thanks
Thanks for all your feedback. I appreciate the time. I did purchase the desk and chair, because I have been wanting the set for a long time and didn't want to deal with Ebay hassles for a large item. I'm a novice at buying vintage, as you probably guessed, so your comments are very helpful!
I think the local market dictates price also, and in my area, great deals are hard to find, unfortunately!