I've got one of these .69 cal. Napoleons I picked up sometime in the late 80's when they were being distributed in America by CVA. The Artilleryman is dead on though, I've seen them listed for a wide range of prices on various different sites. On Guns America for example they're usually being listed in the 500-something to 700 dollar range. I've also seen them on some so called "high class" sites; antique arms dealers and the like, where they're asking close to a thousand.
E-bay, which I'm sure your well aware, is a world unto itself, is another story. As a matter of fact, on an auction that just ended a couple of days ago, a seller had one up for auction that was about in the same condition as your's. The gun was missing the implements, some carriage hardware and had some rust, it sold for 128.00. Generally speaking, right now, these guns are selling on e-bay for anywhere from 2 something to 3 something.
If I was going to sell mine, I'd take the route of going through one of the stores. They'd be getting their 15 or 20 percent off the top but I would still come out ahead.
I can't remember which one it is but either the Antique Cannon Superstore or Cannon Mania displays a contract on their web-site. I think it's Cannon Mania but I'm not sure. Anyway, in the contract he states that he gets 20 percent of the sale price, he pays for all shipping costs and you can advertize on any other site you want to as long as you don't undercut the price your asking for on his site.
It was the Antique Cannon Superstore I was thinking of and now the seller in most cases pays the shipping charges. Cannon Mannia asks for an e-mail request to get the details for selling on consignment through his site.
John