I bought a piece of ground from a widow that was in a rest home, and paid her asking price. But she had an adjoining piece of property and I didn't have the money for both, and I wanted to buy it. So part of my deal was that I got right of first refusal and an option at the stated asking price on the other property. Two years later I sold the first piece for an inflated price, a LOT MORE than what I'd paid for it. I could have bought the second piece for a lot less per my contracted agreement... but instead I sent the lady a card and told her that her property was worth a lot more than it had been two years ago, and I wouldn't be exercising my option.
I gotta say, I have mixed feelings about it. I could have made a lot of money on that deal... but just didn't feel right taking advantage.