Buying used vs. New

Value is established at the point where willing buyer and willing seller converge.

I really can't buy locally. Period. It isn't here to be had.
So that takes care of the shipping damage question because everything-new or used-is going to be shipped.
Scams are another issue entirely and I think you can avoid a lot of that by just not buying without a phone conversation.
Then there's price.

I buy a lot of stuff used because I'd rather let someone else absorb CERTAIN DEPRECIATION while I gamble on having to pay for POSSIBLE REPAIRS.

Either way, when I sell it, it will be used.

Personally, I'm delighted that there are those who feel the need to buy new. They are the nice people who absorb the initial depreciation so that I can buy and sell used stuff with little or no loss. Keep up the good work, guys.

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.

I don't care about the rules that Learsfool sets for himself. There are lots of other better informed buyers for my stuff.
By the way, Zu Druids used to sell new for $2800/pair. The revised model lists for $3400/pair. They both sell instantly for about $2000/pair and have gotten that price for more than 2 years that I have been watching. How does that square with "the formula"?