Jeff,

I would love to see the results of your experiment - I am not at all sure I won't be surprised. Until one measures something, its often like the case of cars: ever notice that when a friend or someone you know has aprticular car in a particular colour, it seems that the majority of them are that colour? Perhaps I am just exposing my insanity here...
I also think you make an excellent point about making the initial decision to sell - with photo gear its a really, really slim chance that you get what the gear is actually worth to you, regardless of what the market value is. Add to that the aspect you mention - learning and getting used to it, and its rarely worth it. Plus, not to sound preachy, but from my (again, very non-scientific) observations most people regret selling their cameras. The return is not that worth while and just see these pages for all the posts that start with: "I really wish I NEVER got rid of that camera..."

Peter.