Yeah, you can get them cheaper, but at best they'll cost as much as a pistol magazine, and they're still only 5 round magz. The price per round will still be double what it would be with a pistol magazine. And don't forget that a LOT of CZ75 or glock17 magz are already in our hands, so technically free.
Our magazine laws are already completely nut, we should at least do the best we can within those laws, and the scorpion really isn't.
Our classification should be different. Instead of pistol and rifle, it should be "range toy" or "hunting toy". Range toy would get unlimited magazine capacity, and hunting toy would get unlimited magazine capacity. That's the kind of classification I would root for.