There are two ways to interpret the relationship between the old woman and the young man. On the one hand, perhaps the young man gained the old woman’s affection through lies and flattery, and then exploited her for money. But on the other hand, perhaps the old woman used her wealth to exploit the young man for sexual and romantic services.
There are a couple of suggestions in the text that favour the second interpretation. First, the young man asked for gifts in the name of his family members:
Chremylus. And what was it he most wanted of you on each occasion?
Old Woman. Not much: for he was extraordinarily shy with me. But he would ask twenty silver drachmas for a cloak, and eight may be for shoes: and he would bid me buy a jacket for his sisters and a small cloak for his mother: and would want four measures of wheat.
Aristophanes (408 BCE). The Plutus, pp. 44–45. Translated by William Charles Green (1892). Cambridge: J. Hall.
So perhaps the young man was the only support for his mother and sisters and sex work was the best of a limited set of options. (Of course, in the first interpretation there were no “sisters” and the young man disposed of the gifts for his own benefit.)
Second, Chremylus says that the young man was formerly suffering from poverty:
Chremylus. Tis plain that in his ways he was not a bad fellow; and later on being rich, he no longer likes lentil;† but before from poverty he would eat anything.
Aristophanes, p. 45.
† There may a double entendre here, as I have seen it claimed that some ancient Greeks considered lentils to be an aphrodisiac. (I have not been able to find primary evidence for this, however.)
Green glosses this line as follows:
‘Plainly he was all along (in the past time) no fool—he took this old woman from necessity, not from choice—and now afterwards having become rich he no longer contents himself with common fare, whereas before he would eat anything.’
William Charles Green (1892). Plutus, p. 77, note to line 1004. Cambridge University Press.
The implication is that formerly, out of desperation, he had to make love to the old woman, but now that he has a choice he can reject her. Summing up, we have the option of interpreting the relationship between the two characters so that the events of the play are just with respect to the two of them.
However, this is not the only way to look at the tension between the “project” of the play and its events. For Plutus does not present us with one project, but two! The play has
a fundamental thematic tension between two quite different conceptions of the nature of want and sufficiency that are phased in and out throughout the argument. The first, in the order of narrative presentation in the text, represents wealth and poverty as a function of unequal social distribution. The rich achieve their wealth at the expense of the honest poor, who are poor because they remain honest. The second conception is predicated on a notion of universal scarcity, as a result of which all alike are more or less indigent. The solutions to these two ways of representing poverty are correspondingly different: the first, or social, conception invites a program of redistribution; the second demands a general improvement in resources, whether through technological progress or a lucky increase in fertility, the extreme imaginative version of which is a return of the spontaneous bounty of the golden age.
David Konstan & Matthew Dillon (1981). ‘The Ideology of Aristophanes’ Wealth’. The American Journal of Philology 102:4, p. 372.
So, under the first conception, it is unjust for the young man to benefit from redistribution given that he had defrauded the old woman, but under the second conception, an end to poverty means that no-one is driven into sex work out of desperation.