Has anyone ever read the book "Predictably Irrational" by Dan Ariely? He's an MIT professor who looks at why people make the decisions they do. Here's a link:
Anyways, he has a chapter about how people tend to way overvalue what they believe is "theirs." He conducts an experiment after a Duke Bball ticket lottery. He asks people who lost what they would pay to get a ticket. The average was around $175 because they were thinking that, although the game would be fun, they could get a lot of other stuff for $200. Because they didn't own the tickets, they had formed no attachment to them, and all other potential possessions held as much value.
On the other hand, he asked people who had won tickets in the lottery what it would take to sell them. The average was around $2,500 because people felt the tickets were "theirs," and started to value them more. The point was the difference between what people would give up and what people would have to give up was huge.
Dave touched on this when he talked about how we are never no way no how ever getting Chris Paul. How many times have we read that "Jack + Trout + 13" could net us Rose? Yet if you look at it objectively, there is no way that would happen. Would you take two bench players and a low lottery pick for a potential Hall-of-Famer?
This is why so few trades actually ever happen. And a superstar getting traded is usually an act of desperation where one team gets completely screwed (See: Minnesota, Memphis, Phoenix, Dallas etc...).
This doesn't mean that a deal can't get done. Just that what we have isn't nearly as valuable as we think it is.