I think you see a problem where none exists.
The best paid players are more often than not, not the best players. The best players are the players with the most skills, not with the highest salary.
If you dont see the difference or imbalance between the trainings-skills around outside players and inside of course then you dont see any problem.
The secundaries skills trained on a outside player are still really cheap related to the effect they have on the game engine, that its usually really high. You can argue that its the same for the inside players, but the fact is that is really easy to train a SG-PG, with 22 years you can have a multiskilled player with a ''low'' salary and if you compare it to an inside player, that player is really difficult you train them on passing, JR, OD etc or it takes much longer...
The training of an outside player is really easier than the one in inside(if we are talking about multiskilled ones), thats the fact i suppose lot of managers only train IS-RE-ID. The only training its ok for them is JS-1vs1 in SF-PF if you consider that 1n1 is important.
Not to talk about small-forwards that are usually trained in all skills, with a 0 cost on secundary skills...
This salary formula is in general really bad and having the TL low doesnt help