Depends on how the barrel is choked. I bought a field grade 28 gauge with a vent rib and choked full. I paid $395, and sent the barrel off to have it reamed out to IC. Blue Book says $295 for 98% and then subtract $40 for barrel without VR, but I think the market is out there, and you could get more than that. $300-$400. Mark
Looking at completed auctions on gunbroker, it looks like the VR skeet guns are averaging the mid 700s. One only got bid up to the mid 200s and didn't meet its reserve (another example of why reserve auctions are a bad idea, another one @ $250 got no bids because of the reserve). Only ones going for $1k are the Sporting 28s w/ screw chokes.
So it looks like I was a little bit under market (gunbroker) value, at least not as much as the Blue Book LOL.