We seem to highly regard DEMO over anything else.

Amps and preamps don't worry me but speakers may be prefatigued by overdriving or worse yet underdriving.

I bought 6 month old demo speakers for 60% of the price. They have full factory warranty and sound wonderful.

"The majority seem to regard demo equipment more desirable than anything else, used. Could someone please tell me why?"

Its a safer purchase. There's all kinds of risk buying from private sellers. You're much less likely to have any problems when you use a dealer. Also, with a private seller, you have no idea how many times the component changed hands. If you've ever read some of the threads on this forum, you'll find that there's quite a few people who constantly buy used equipment to try it, and sell it a short time after. It may have changed hands 20 times, for all you know. Would you feel comfortable buying something that UPS/FedEx used for a soccer ball 20x? For a good description as to what I'm talking about, watch the beginning of Ace Ventura.

"I know there is a warranty but I have never had a piece break down in the first 2 years ."

Past performance is no guarantee of future results.

I have bought and sold quite a few times myself. Fortunately for me I have been very lucky with shipping and receiving. Only two pieces have been demo and I sold them fairly quickly as I recall.

I don't maybe you do.