Everyone is different, this is my daughter's favorite saying, but for what it is worth, here is my ethical line: If it is marked a dollar and I know it is worth more, even a couple of hundred, I buy it for the dollar they marked it. For all the reasons mentioned here such as they could have done the research, I have put the time into learning this, the connections to sell it or the time to list it on eBay and etc. If I buy more at the same yard sale, I will try and stop myself from asking for a "bundled" price on stuff knowing I already have a great deal. If the people really look like they need the money I will force myself not to bundle. On the other hand. If I have to ask the price on something and someone says, "What's it worth?" and I can't get them to give me a price after asking several times, I can't seem to help myself from being honest and telling them a low-ish fair market price, but telling them I can only give half of that. That usually leaves me more than enough room to make some money and is how I sleep at night. I try very hard to let or make them set the price. I too have paid more than what was asked for items, especially coin collections that were worth a ton more that were offered to me for $50 or "would you give me a hundred for these?" and I have a very few times paid more than what was asked or even returned with more money. I guess some of you will laugh at that, but one time a neighbor sold me his coin collection, his dead father's actually, and at the last minute threw in a small bank he said contained just some wheat pennies from his father's pocket change over the years. He was right for the most part, but it also contained a large cent, a 3 cent piece and a two cent piece. I took them back down to him and told him what I had found and left him another $40 dollars. Am I a fool, perhaps, but I made money, we still are on good terms, and I feel good about it. Like my daughter says, "Everybody is different."
T.