Lets start it cheap... I.E. no KPs.
I ran across a 14" ACI barrel which I believe was intended for a Maverick at a local store that doesn't specialize in paintball. It's unused as near as I can tell, and has a little ring that extends 1/4" out about 5 inches up the barrel from the threading. It was $0.99 so I bought it, in all good conscience can I sell it for more?