How Much is the Price of a Domain Name that has no Traffic?

Hard to say. Depends on how good / popular / easy to remember domain name. Although it has no traffic, the owner might be looking to develop something in that domain later. It could also be someone who parks domains for profit and selling to people who ask. It could also be a business that went out of business. 
 
So in general 

It is difficult to give a price range for the domain, we do not know how good it is. I would say that a domain useless (a small company that sank without visitors and bad name) would be close to free (under $ 20), but it is a good name that is just parked, it could be thousands of dollars despite which has no traffic today.