This is sort of a spin off from the Guild thread I started for a friend, and all of the responses from that thread have been appreciated and were most informative.

In the process of acquiring this 1978 Guild G212NT, which my friend did, it struck me about the ethics of buying a vintage or rare instrument when the seller doesn't appreciate the value of an instrument, or, is hard up for cash.

She did buy the Guild, and knowing its current true market value, which we found out both through a combination of the comments here, as well as talking to a few knowledgable stores, is in the neighborhood of $ 950.00 - $1,000.00 (U.S.), she initially offered the seller $300.00 just to test the waters (and with a very good poker face), and he came back with a counter offer of $335.00 at which point she couldn't get the money out of her purse fast enough, and then leave.
Yes, it's a great deal and as far as I am concerned she practically stole the instrument. But the seller got what he wanted.

Should one feel guilty or that they are taking advantage of the situation, when something like this comes along?

Or should one simply be pleased that they found a rare deal and were fortunate enough to be able to act on it?