I thing its a workable stragety to allow one star per team, I actually posted before sam signed that it would be an idea to allow 1 british player on each squad to only count 33% of their salary towards the cap.
That way, taking into account some clubs not spending up to the cap, there would be about 10 spots available in Superleague where star players could be protected from the clutches of Union and NRL, (hopefully) without allowing clubs to blow a crippling amount of money on multiple high wages.
Now, if Sean O'Loughlin was upset that Sam had/has said spot at Wigan and was earning a lot more than him, then it is his choice to try negotiate a similar contract at another club.