I am headed over there now to look for it, but you might try the Brownell's web site for that information. They take a survey of standard gunsmithing costs and have it in their catalog - not sure about the web site.
There are of course different metods of getting the same job done - some lower tech that others, and with a bit of patience and reason that low tech approach can work out just fine. I have cut a few barrels in my day using different techniques.
Old Fuff and others have valid points for you to consider - not everyone can just hacksaw off a barrel and get it squared up, and the crowning true to the bore without having some equipment or special skills/knowledge. Sometimes the cost can exceed a flat out barrel replacement or gun trade.
Amoung gunsmiths the cost will vary widely . Sometimes because of how they do their work, and sometimes just because. To cut a barrel shorter is not rocket science for sure, but to do it right takes more than a pipe cutter or a hacksaw. You at least should have a file ! LOL
Depends on finish work as well, and the hardest part can be re-mounting a front sight. Good luck, and like I said , I am headed over to Brownells web page to see if they post that gunsmithing average charges thingy there. WIll give us a better idea perhaps.
EDIT: Didn't find it at the web site but according to the catalog I have here a survey of gunsmithing prices would be : $35 to $95 to cut and crown the barrel, $50 to $75 to sweat on a new front sight. This does not include any refinishing. You can see the cost has a good wide variance .