You are assuming symmetries where there are none. I want a thing, discover it's readily available for $1300, that seems insane, so I don't buy it. By chance I acquire the thing from a source that was unaware of its fair market value for $2, amazing deal. I have the thing without having to pay an insane price, I am happy. Now here comes an insane person who wants it enough to offer me $1300. Both parties must benefit from an exchange for there to be a transaction, but the benefit is always subjective to them, depends on public and private information, there's no symmetry in buying/selling, and the equations have inequalities rather than equal signs. Now if the offer is sufficiently higher than $1300, or I know I can find the thing again for sufficiently less, or I find myself in need of the $1298 unrealized gain for other things, then sure, it becomes insane to not sell, but absent such factors refusing a fair market offer at a price you wouldn't ever entertain paying yourself is not insane. Additionally, prices aren't static, platonic things. If someone is insane enough to offer $1300, perhaps they are insane enough to offer $2600 in a year, I will be enjoying the thing in the meantime.