Well, I guess I'd have to say I've seen a picture of one, now. 8^) $148 isn't all that bad considering how much you'd have to pay for a good used 18- 18.5" barrel plus getting choke tubes installed. And if you want choke tubes in a short barrel, well, that's been the only option I know of till now.
Given how good buckshot loads are these days, though, you can pretty well pick your pattern by picking your loads. Anything loaded with a FliteControl wad (Hornady TAP, Federal LE and Premium loads) are likely to give very tight patterns even out of open chokes. The middle ground loads (Remington, Winchester, Fiocchi, Federal non-Premium etc.) will likely yield moderately tight patterns depending on the load and the gun. And the least expensive loads (S&B, Rio, etc) are likely to throw wide open patterns with their soft lead, non-buffered, unprotected buckshot. And you don't even have to change choke tubes to vary patterns a good bit as a usual thing.
Of course, every shotgun barrel is different and it's impossible to predict with confidence what any specific barrel and load will do. It takes patterning to tell for sure. But in general, I have found the above to be true with several shotguns I have experimented on.
As Scattergun Bob says, the most uniformly beneficial modification I have found for improving buckshot patterns so far is to have the barrel's forcing cone lengthened.
lpl