Joan Robinson quote: “the merchant had observed that the marginal utility of daughters decreases with surprising rapidity.”

“Part of it, which perhaps you and most other observers are not aware, is that I have enough passive income, and enough dispassion for conventional status signaling, that my marginal utility of money is pretty low compared to my disutility for doing busywork.”

Wei Dai Cryptocurrency pioneer and computer scientist

To put it in perspective, I quit my last regular job in 2002, and stopped doing consulting for that company as well (at $100/hour) a year later when they merged with Microsoft and told me I had to do a bunch of paperwork and be hired by Microsoft's "independent consulting company" in order to continue.
In a discussion thread https://www.lesswrong.com/posts/Jter3YhFBZFYo8vtq/look-for-the-next-tech-gold-rush#ikKBYevf2aL2pBwsS on LessWrong, July 2014

“The first problem I propose to tackle is this: how much of its income should a nation save? To answer this a simple rule is obtained valid under conditions of surprising generality; the rule, which will be further elucidated later, runs as follows.
The rate of saving multiplied by the marginal utility of money should always be equal to the amount by which the total net rate of enjoyment of utility falls short of the maximum possible rate of enjoyment.”

Frank P. Ramsey (1903–1930) British mathematician, philosopher

"A Mathematical Theory of Saving", The Economic Journal, Vol. 38, No. 152 (Dec., 1928)

“One of the most important axioms is, that as the quantity of any commodity, for instance, plain food, which a man has to consume, increases, so the utility or benefit derived from the last portion used decreases in degree. The decrease in enjoyment between the beginning and the end of a meal may be taken as an example.”

William Stanley Jevons (1835–1882) English economist and logician

William Stanley Jevons Letter to his brother (1 June 1860), published in Letters and Journal of W. Stanley Jevons (1886), edited by Harriet A. Jevons, his wife, p. 151 - 152.

“The utility of a language as a tool of thought increases with the range of topics it can treat, but decreases with the amount of vocabulary and the complexity of grammatical rules which the user must keep in mind. Economy of notation is therefore important.”

Kenneth E. Iverson (1920–2004) Canadian computer scientist

§1.4
Notation as a Tool of Thought (1979)

“One of the most important axioms is, that as the quantity of any commodity, for instance, plain food, which a man has to consume, increases, so the utility or benefit derived from the last portion used decreases in degree. The decrease in enjoyment between the beginning and the end of a meal may be taken as an example. And I assume that on an average, the ratio of utility is some continuous mathematical function of the quantity of commodity. This law of utility has, in fact, always been assumed by political economists under the more complex form and name of the Law of Supply and Demand. But once fairly stated in its simple form, it opens up the whole of the subject.”

William Stanley Jevons (1835–1882) English economist and logician

Letter to his brother (1 June 1860), published in Letters and Journal of W. Stanley Jevons (1886), edited by Harriet A. Jevons, his wife, p. 151. https://archive.org/details/cu31924074297254/page/n168/mode/1up

“I approached the problem of utility measurement in 1923 during a stay in Paris. There were three objects I had in view :
:(I) To point out the choice axioms that are implied when we think of utility as a quantity, and to define utility in a rigorous way by starting from a set of such axioms;
:(II) To develop a method of measuring utility statistically;
:(III) To apply the method to actual data.
The results of my study along these lines are contained in a paper “Sur un Problème d’Économic Pure”, published in the Series Norsk Matematisk Forenings Skrifter, Serie I, Nr 16, 1926. In this paper, the axiomatics are worked out so far as the static utility concept is concerned. The method of measurement developed is the method of isoquants, which is also outlined in Section 4 below. The statistical data to which the method was applied were sales and price statistics collected by the “Union des Coopérateurs Parisien”. From these data I constructed what I believe can be considered the marginal utility curve of money for the “average” member of the group of people forming the customers of the union. To my knowledge, this is the first marginal utility curve of money ever published.”

Ragnar Frisch (1895–1973) Norwegian economist

Frisch (1932) New Methods of Measuring Marginal Utility. Mohr, Tübingen. p. 2-3: Quoted in: Dagsvik, John K., Steinar Strøm, and Zhiyang Jia. " A stochastic model for the utility of income http://www.ssb.no/a/publikasjoner/pdf/DP/dp358.pdf." (2003).
1930s