Without question JS is the most lucrative skill to train if you are trying to make money on the TL. People will overpay for OD, but usually the player must be decent all around to sell. There are 50000 users playing this game, and at least 30000 of them think, "Wow, high jump shot, this guy is great!"
One of the great misconceptions of the game, and a point to take advantage of if you are into working the TL.
The other misconception for me is the potential lust that people have. Unless you are going to single train a player, anything over Allstar is a waste of money. That is off topic, I know, but I wanted to say it anyway.
Once I scored a basket that still makes me laugh.