Yeah, I noticed this too. Fortunately, right now, I'm in pretty good probe shape though. But, as you say, listings for used stuff where the price on Keysight for new is half what they are asking?
Try this on eBay; search for "Agilent" and then sort results by highest price first - the first 4 or 5 items are 'buy it now' for $999,999.00, you do get free shipping though!
That seems like it must be some kind of calculation error - perhaps the Taiwan poster entered a number that got translated badly by eBay?