Any form of " capping " would simply reduce the number of players and in turn generate money for the potencial winners .
As the game is obviously a game of chance with the opertunity of a life changing amount of money to be had by one or two lucky people , this is a way to encourage higher sales and therefore higher prizes as well as higher income for the good causes and tax man.
I know im the one here always putting the idea's down , and im sorry for that , its just that i can see why the idea's put forward " so far " could not work. I wish i could see a way round this myself so i could actualy give a possative answer to this question instead of the current always negative's, but sadly as of yet i am unable to see a viable alternative