Well, I guess you are right, it wouldn't cost that much, however, it would still start those player's clocks ticking wouldn't it? Over the long term, I think it could have a much larger impact on your salary structure....
Also, would it really dumb down the game? Let's be realistic, most teams would only have 2 or 3 players at most they want to move between AAA and ML, and those players would not exactly be all stars types. Some teams may have as many as 5 perhaps... In fact, it would reward teams that actually build their teams the right way, and have a strong minor league system...rather than those owners who ignore their minors and just buy a great ML team, damn the future. Wouldn't that be the opposite of dumbing down the game?