What determines "market value" or a "fair price" for anything? Do you go by yesterday's price? Last week's? Last month's? How about next week's? It still comes down to a balance of what one is willing to take for an item vs. what another is willing to give. If someone is willing to take less than you're willing to give, there's a likely chance that someone else will give what he's willing to take before you, thus establishing the "fair market value".
It's fine if you like to pay more for something than people are asking. There's no harm in that, but neither is there harm is paying what one is asking at the time they are selling, even if you think it might be worth more (to you).