At the moment, it would be reckless and detrimental to the competition to raise the salary cap just to please a few clubs such as Saints, as about 8 clubs would struggle to manage a higher salary bill (just look at the financial results this year of Hull KR and Crusaders) and then there will be clubs losing top players to stronger clubs at a higher rate than we already have.
As for McManus and Graham, I can understand McManus' concerns and why he has spoken out. He is running a business and if the top players leave not just saints but the other Super League clubs, the competition can lose appeal, therefore could impact sponsors and supporters. Graham has never hid the fact of a desire to play in the NRL and who can blame him? The NRL is the biggest competition and every week is a huge challenge.
For England internationally it is better that these players are going over, for saints and super league its bad news. The only way to have some sort of prevention to this is the clubs who nurture the players such as Graham, Roby, Ashton, Burgess, Tompkins etc receive compensation, unfortunately to do that it would become all legal and through courts etc.