[raulus]

I think the reason why the sunk cost fallacy exists as a phenomenon is because humans are often illogical and emotional, in spite of our better judgment. That and we hate to lose money and/or experience pain. Studies have consistently shown that people will routinely choose illogical options if it means that they can avoid loss/pain.

The other element is that we are all perpetually optimistic when it comes to our items. Just because it's down today doesn't mean that it will be down tomorrow. And if I'm convinced it will be back up tomorrow, then I'm less inclined to sell today unless I feel like I'm getting tomorrow's price.