I think it's $250-$300 overpriced. He probably paid around $900 new. The triggers on these O/U's tend to be pretty heavy and it will be heavier than a dedicated 28 ga. O/U. Unless you want/need both a 20 ga. and 28 ga. gun, I'd hold out for a 28 ga. or make a lower offer .
I saw somewhere that the triggers got good reviews. There are advantages to having a 20ga 3" gun along with the 28ga, even though the 28 is a bit bigger than most 28'.