It's only what the market will bear, and it cuts both ways. Pre-Bosman condition was de facto market intervention at odds with normal, modern labour conditions.Bosman changed everything, no doubt. We went from a game where the clubs took advantage of the players, to a game where the players take advantage of the clubs.
Football has always been a particularly mercenary game.
It's therefore impossible for either party to take advantage, as you say. If one party takes a gamble then you might end up with a Leeds United situation. That was more the fault of Ridsdale than Danny Mills.