Hello AP
The rug you are requesting feedback on is a very, very large piece and could very well be worth every bit of $40,000 and maybe even more (or even less.) According to the seller the rug being offered is in "perfect condition." The problem with this, however, is that from rug person to rug person, "perfect condition" can mean anything from "looks great for its age" to "it is in
perfect condition." There is no set standard.
Here is an assessment:
Regarding the signature - while this may or may not be a "Tafshanjian" signature, in most cases, a signature will do little more than reinforcing a place and time the rug was woven. There are rare instances however, when specific signatures help attribute the piece to a rare workshop or particularly exceptional quality standard of importation which may have an affect on value.
Reviewing the quality of the wool is not something we can do over the internet very easily, but there is a good chance this could be of a finer quality. Although the rug looks to be in great shape, we cannot tell without very close up photos either. The carpet has a significant amount of pink overtone, and also features heavy inscriptions in a banner around the double mihrabs of the carpet within the field. These are the only two things the rug has going "against it." In other words, although the rug may have a high value for what it is, the design and overtone may make it a tough sell - you may have bargaining room with this rug.
Inquire further specifically regarding condition. If you are serious, let the seller know this to be the case. It will encourage a more accurate overview of the rug - maybe even let him know you are interested in visiting the piece. Although the seller states the rug could be in perfect condition (and it very well could be) make sure to ask if the rug...
1 appears to have ever been used or low areas
2 has any color run
3 has moth damage, areas of missing pile, repairs, dry rot or other
4 has any matting or blooming of the wool
Finally, if the rug passes all the above, go visit it in person prior to purchasing. You want to make sure the rug has been described 100% accurately, and even smell the rug to make sure there is no unusual odor. There are certain aspects of rug wear which one cannot tell unless good photographs has been produced to see these things. There's nothing wrong with purchasing a carpet that shows signs of use: but there is something wrong in paying an amount which is supposed to purchase a rug in perfect condition, and finding it has been used.
Helpful Links:http://rugrag.com/post/Authentic--Signed.aspx
http://rugrag.com/post/Pile-Height.aspx
http://rugrag.com/post/Color-run-.aspx
http://rugrag.com/post/Condition.aspx