Bingo. I was about to say what acdodd just did.
You guys are thinking like gunnies. To figure out a criminal mind, figure out his environment.
Let's say you're the thief. You break in. There on the wall is a Beretta 682 marked at $4k. You grab that gun. The length of the gun makes it tough to slide back down through the hole in the floor. Takes you a little longer to get out of the shop. then you need to stuff it in the car so that it can't be seen. Also tough with a long gun. Then you want to sell it. Sell it to a legit place, and you'll arouse suspicion. Sell it on the black market and you get no more than you would for any other cheapo shotgun, because ghetto-bubba is gonna cut off the stock, and take a hacksaw to the barrels to turn it into a sawed-off shotgun. Ghetto-bubba has no interest in a quality trap gun.
On the other hand, lets say that you go into the store, and grab a Glock 22. You can stuff it in your waistband, crawl out, hide it easily, and make big bucks with it on the street because it's exactly what your target audience wants. I have no way to prove it, but I'd bet that in da' hood you'd get more money for a Glock than for a $4k trap shotgun.
These weren't stupid criminals. They were savvy, and playing to their crowd.
I could probably stuff a backpack with what, 20? 30 semi-auto handguns easily? If each of those brings me even $300 on the street, that means I make $6-9k in gun sales.
Not that I would ever break the law, or advocate that anyone else break the law, but if I were these criminals, I'd do the same thing. Go for the guns with real street value.
A private guy selling many multi-thousand-dollar shotguns, rifles, and pistols raises eyebrows.