It's simply a matter of supply and demand. If people didn't want them, they wouldn't sell for as much. But they do - they're light, they're nice looking, they have the right offsets and such, and they work perfectly with the '94-01 OEM tires.
Stop and think for a second. You are complaining because you obviously really want these wheels, probably for some of the reasons stated here. What makes you think that no one else would want them, so that people should be willing to give them away at a steep discount? (Remember, a new set still costs $2800 with the best discounts around.)
What I find surprising is that the '91-93 stock wheels sell for so little (actually, about half the price you quote), not that the '94-01 sell for so much.
Anyway, prices are set in the marketplace, by supply and demand. Obviously, supply and demand balance each other out at a different price point for used '94-01 stock wheels than for used '91-93 stock wheels. If you think that new aftermarket wheels provide a better value for your money, then buy them instead of used stock ones!