A lot of what you see in the specs is just marketing - in my mind there is little, if any, difference in the best guns for Skeet, Sporting Clays and bird hunting. For me personally, I use exactly the same O/U - in all 3.
+ - $ 400 / on a $3,000 gun is about 13% - so you'll probably find different chokes included with some guns ( they're $50 - $60 each), you may see ported barrels, a little better figure in the wood, maybe an adjustable trigger, maybe some scroll work or engraving, some have different barrel length options, ... / and all that relates to price / and demand, etc ... / is the price justified, probably yes / but no way to know for sure. You have to be the judge as the buyer on that issue.
Personally in an all around O/U, I like a gun at about 8 1/2 lbs, 30" barrels, preferably ported, extended chokes, a decent piece of wood on it, a rib with a mid bead, type of front bead is irrelevant to me - and ideally a parallel adj comb.
Trap is different / and when you go to a dedicated Trap gun - I want a gun up around 10lbs, 32" barrels in an O/U.