Audiogon purchase: too good to be true?

Well, if he is a deaelr, what is the business name? Get the business phone number off web... call them.
Find out rom the manufacturer is that dealer actually an authorized dealer for that product.

The markup on some power conditioners is more than 50%.
So even at half price, he may still be not losing money.
It may have been a special order for a customer who changed their mind, and lost the down payment. So th dealer can sell it for less...

Or the person may not be a dealer and selling a grey market unit. And his promise of warranty is a lie.

if it's sold for $2k than perhaps its actual price is $1k

If you exercise your due diligence as suggested, it should be easy to verify the legitimacy or not of a dealer.

Elizabeth is correct. I have had several dealings like this over the years, though normally, the dealers prefer this to be a discretionary transaction, so I do not publicize it publically on the internet.

Also make sure the device is actually worth whatever you pay.

Discounts off advertised retail prices are often not a good indicator of actual value in the end. Retail price may be set mainly for marketing reasons. Then when real value of product becomes known, it appears to be a great deal where in fact it is not necessarily any better or worse than any other.