There's nothing wrong with the idea of an internal utility calculation. The problem comes in when people try to compare or sum utility across multiple individuals. I might have a personal utility function which says an apple has higher utility to me than an orange, while your personal utility function says just the opposite. It makes no sense to try to mix these together in an attempt to estimate just how much apples or oranges are worth to the two of us collectively.
Money is a reasonable approximation of "aggregate utility" most of the time, but that holds only so long as interactions between individuals remain voluntary and there is enough trade in similar items to establish a "customary price". It doesn't work well for goods which are not customarily traded for money, or as a basis for orchestrating involuntary interference in the market.
Money is a reasonable approximation of "aggregate utility" most of the time, but that holds only so long as interactions between individuals remain voluntary and there is enough trade in similar items to establish a "customary price". It doesn't work well for goods which are not customarily traded for money, or as a basis for orchestrating involuntary interference in the market.