The 1967 Shelby GT500 is undoubtedly the most desirable production Mustang in the world. A well done recreation of this car, or clone will usually cost between $50,000-$80,000. A genuine example would bring at least $200,000+.
If you want a real Shelby, you should know that 1968 and newer GT500s are significantly cheaper than 1967 models because more were made. You can also get a replica of the Gone In 60 Seconds "Eleanor" car for around $70,000.
A decent one is going to cost between $50,000 - $75,000. Even more if you find one that has been professionally restored or in mint condition.
The cheapest one on EBay right now is $51,000. It is doubtful that this car has met its reserve price. I expect this to go a lot higher before the bidding is over. They have one with a "Buy it now" cost of $219,900. I expect this to be more typical of the cost of a decent 67 Shelby.
I have seen these sell on Barret Jackson for close to $1,000,000
shopping for fun on road trip we found out the shelbys were WAY more than the regular mustangs. In pricing cars and stuff for reselling my mustang the specialty cars seem to fetch a lot more thna a plain old car. http://mustangmustle.blogspot.com/