It's not meant to be scientific. It's a tool for abstracting a situation down to understand the intent rather than the details. Your first mistake here is to

It's not meant to be scientific. It's a tool for abstracting a situation down to understand the intent rather than the details. Your first mistake here is to try and assign a '$X worth of utility' - utility is not a unit which can be expressed in another unit. Someone can spend $x on something which gives them utility, but equally they can go for a hike in the mountains which provides greater utility to that individual than the object bought for $x, yet the hike costs has no $ value and cannot be bought nor sold. So the circular argument criticism is only circular because you're forcing it to be circular.