Buying used vs. New

I agree with Tvad. Rigid policies are inappropriate in the face of inconsistent circumstances. There is no formula that can be applied universally since every situation is different. Factory direct products with strict pricing policies like Red Wine Audio maintain a very high resale in the neighborhood of 75%, whereas the Talon Khorus was dumped into the marketplace and now sells used for maybe 25% of list price.
I don't think the resale percentage of these products reflects their relative value or desirability.
Some vintage products fade into oblivion only to be rediscovered eventually and then their selling price soars due to scarcity. Certain turntables from Lenco, Garrard and Technics bear this out.

LOL, many items sell for more money used than they did when new, Quad ESL57s, Rogers LS 3/5A, EMT turntables, most vacuum tubes, better Garrard and Thorens tables, the list would take up pages.

Rigid policies are inappropriate in the face of inconsistent circumstances.

Macrojack,

Do you work for a pharmaceutical? This statement bears resemblance to the warning "if it lasts for more than 4 hours contact your doctor"...(why a doctor, in particular, should be open to such overtures I just can't figure out)

Yes, of course, there are certain items, particularly vintage ones like the Garrard and Thorens mentioned, where you will have to pay more, and it would be worth it to do so. And there are other exceptions that don't have anything to do with the actual value of the item, as someone mentioned. However, the 50% rule I stated does hold true for the vast majority of products out there in any high end industry, whether it is audio, jewelry, cars, what have you, and many people in all of those industries will agree with that. Yes, you will see people here on audiogon paying more, but they certainly don't have to, and in the vast majority of cases shouldn't be. You also see many items not selling either here or on ebay because they are priced above this mark. Very often, the seller has to come down to near that 50% before anyone even bids. Is this a hard and fast number? No. Is it a good general rule of thumb? Yes.

Not sure I see much value for the 50% rule with used audio gear. There are too many factors that come into play.

I would be comfortable saying that the more you pay, the more you should be certain you have good reasons for paying it.