Over a long enough time-span it isn't zero-sum. Under any sort of limited time span, which is what people with limited amount of life live deal with, it is zero-sum. It doesn't matter how much money you spend, the economy has material and man power limits than cannot be exceeded no matter what someone manages to pull out of their butt. On top of that, the value of money IS affected by the total amount of currency in circulation as history has shown many times over, and only in a theoretical economic vacuum where customers are infinite does one guy holding a trillion dollars not devalue someone else's $1.