Given that we have already removed all the crazy people I am sure you will have no problem grasping that the percentage is pretty much set when you play at a casino and your cash to spend is also set. It follows then that if you double your cash the percentage will still be 98% or 2% to the casino. However when you take advantage of a casino bonus and you double your initial stake money you have been given free cash. This means that you have half your money that was not yours so you have a 2% ex...