Because you could touch and look at them before buying? And there's that tax and shipping issue.....
It's true, though, that most folks here are offering fatter discounts for their takeoffs and mistake purchases. If the discount isn't perceived to be enough to be "fair" (whatever "fair" is), then it won't be a quick sale. It's a self-regulating problem.
Heck, on trailvoy, somebody would post a picture of a wrecked SS, and within minutes some vulture would say: "Hey, those rims don't look damaged....how much for them?"