According to the economists’ equation of maximization of utility the ratio of marginal utilities of two things is the ratio of prices of the two. When this point is reached one gets the maximum utility from both the things. In any case the utility of a thing to an individual may be measured by the money price he is ready to pay for this. Yet what applies to material goods does not apply to non-material goods such as love, beauty and honesty. You are never satiated with beauty or true love. You have a human capacity to love all.

To follow Pareto (1968, 168):

For an individual, the ophelimite [his term for marginal utility] of a certain quantity of a thing, added to another known quantity (which can be equal to zero) of this thing already possessed by him, is the pleasure which this quantity affords him.