Legalize everything and you will increase costs to taxpayers in my opinion because of government being in the welfare business (which it has no right to be in), even though keeping the war on drugs is costing me as well.
Yet there in lies the problem. You already pay the costs for the drug culture. Those likely to use currently illegal drugs either already do so, or use alcohol and tobacco. It's part of the mentality. So, you pay for both the war on drugs and the costs of the current drug culture. The point being made by others is that once we admit that the war on drugs was lost long ago, we stop paying for the war, and only pay for the drug culture.