I think we are on the same page when it comes to "more talented players" being able to better adapt to a new system. It is probably what helped to make them a better player. Take Aaron Rodgers for example. He is playing a very complex position at a very complex level, but I have full confidence that he could play at a high level with almost any team. How long would that take though? Just the off season or a few games? If Aaron Rodger was on the open market today, what would his perceived VS. actual value be to the Packers as opposed to the Cleveland Browns?
But if you take a guy like John Kuhn and place a value on him, I think that value is higher to the Packers then it would be for most teams. Also I am not equating "value" with final contracted amount (perceived value). I think that is where we see TT step out of the picture and say "fine, you can have him, your perceived value is higher then ours."
You are also right, many teams make the mistake of over valuing their own players for various reasons. However, this is done even more frequently in the Free agent market IMO. I still contend that a GM's job of determining his own players value is easier then trying to determine the value of another teams player being brought over to his team. Sometimes this value can be higher, as I think it would be in Kuhn's case. John Kuhn has/had become an intricate part of the Packers offense, would he be able to recreate that with another team and QB? Basically, there are 11+ moving parts on the offense and if you took 1 of those parts out and substituted in an equally talented but unfamiliar part, logic would say, things will change.