There are often deals on broomhandles on GB, you just have to watch for them!
$750 I would say is the most for a decent amount of original rifling, though $650 would probably be my limit for the finish on yours. For a project gun I would probably look for no more than $550. You can occasionally find a junker in the $300 dollar range, but they could be a real gamble.
http://www.gunbroker.com/Auction/Vie...Item=268205015
http://www.gunbroker.com/Auction/Vie...Item=272057648
http://www.gunbroker.com/Auction/Vie...Item=281413567