Here is a thread that was started a few months ago about the cost of Yorkies.
http://www.yorkietalk.com/forums/gen...ur-yorkie.html
Also, there is a lot of price difference based on where you live and how close to the Yorkshire Terrier AKC standard they are. No offense but you are going to quite a big man on your hands, if he is 6 lbs at 18 weeks. They cannot be over 7 lbs to show and should not be bred if they are over 7 lbs.