The value of water to a person dying from dehydration is infinite compared to someone who's adequately hydrated. By that logic, this bottle of water is worth every possession, good thing, in the present and in perpetuity because that is the opportunity cost. Nobody would choose $50 million in cash to reject the water because the money only has value if you take the water.
But hypothetically, if the value and the price could be finitely defined, a "fair trade": let's say 10 apples and 1 watermelon are each worth 10 utility units. Price still can't equal the value. We don't eat utility units. The watermelon inherently provides a different value than the apples. An apple isn't a substitute for a watermelon.
I think this is my long winded way to conclude that trying to compare everything is apples and oranges, but somehow we still try to give it a dollar amount.