You might increase your customer base if you also dealt with smaller cannon, say 1/2"-3/4" bore.
Here's my 1/2" cannon I cranked out in a couple of hours when I had my lathe:
Of course, many who have a lathe could produce one of these pretty easily, but just think of all the Independence Day bangers who don't, and would like one of these for, say, $75-$100 or whatever.
The wheels got knocked off from recoil, but have been replaced since this pic. The shot is just for show --they're actually .44 lead balls from an 1858 Remmy I had.
Terry, 230RN