Don't write off buying a fine antique British hammer gun for $4,000, particularly if you are willing to buy quality and not the name, Damascus or sleeved rather than original steel barrels. No one offers a more reliable product in this space than Toby Barclay of Heritage Guns. Here is a very nice hammergun for under $4000:

http://www.heritageguns.co.uk/Williamson%20RUL%2012/Williamson%20RUL%2012%20Details.htm