Workers being paid a just wage is a major element of the social teaching and is something that all Catholics need to understand and be supportive of as it is directly connected to the respect for human dignity that underlies all of the social teaching.
This article from Inside Catholic is a good examination of it.
An excerpt.
“…The Worker Deserves His Wage
“Since we've established that the state can intervene in the economy in order to promote the common good, the next question is, what is the teaching of the Church regarding the wages of workers? First, the Church observes biblical admonitions such as Deuteronomy 24:15:
“You shall pay him [the hired man or servant] each day's wages before sundown on the day itself, since he is poor and looks forward to them. Otherwise he will cry to the Lord against you, and you will be held guilty.
“In view of this passage and others, such as James 5:4, the Church has taught that depriving a worker of his just wages, whether by withholding them or failing to pay a just wage, is gravely sinful (CCC 2434), and in fact has called it one of the four "sins that cry to heaven for vengeance." This is the case, as Leo XIII wrote, because "the laboring man is, as a rule, weak and unprotected, and because his slender means should in proportion to their scantiness be accounted sacred" (RN 20).
“Workers are due their wages as a matter of justice. The Catechism tells us that "a just wage is the legitimate fruit of work" (2434). But a just wage is not that which will merely provide sufficient food, clothing, and shelter. To live at a subsistence level is to live at the minimum condition of human dignity, and, as St. Thomas Aquinas wrote in the Summa Theologica, "No one is obliged to live unbecomingly."
“A just wage, then, should provide a worker with enough to live, and perhaps a little more, so as to enable him to live "becomingly." The Church has, therefore, always desired that the worker not remain trapped at a subsistence level, but be able to better his condition: The degree of independence the worker gains by doing so increases his dignity, which is part and parcel of living becomingly. To obtain property, then, whether in the form of real property or durable possessions, is a principal object of every worker. The worker, by living "sparingly, saves money, and, for greater security, invests his savings," and has the "hope and possibility of increasing his resources and of bettering his condition in life" (RN 5).
“Pope Pius XI, 40 years after Leo XIII, elaborated on this theme in his social encyclical Quadragesimo Anno, saying that by accumulating property, workers can emerge "from that hand-to-mouth uncertainty which is the lot of the proletarian. Thus they will not only be in a position to support life's changing fortunes, but will also have the reassuring confidence that when their lives are ended, some little provision will remain for those whom they leave behind them" (61). This principle led John Paul II to write that the accumulation of property is necessary "for the autonomy and development of the person" (CA 30).
“Apart from the worker's own dignity, though, there is another practical reason to pay the worker a decent wage, which even the most hard-nosed capitalist could embrace: By becoming more substantial citizens, people are no longer plagued by the feelings of hopelessness and dispossession that often characterize the lives of the poor. A man with property has a stake in his community; he is rooted, as it were. A man with property is more inclined to look to the future and make provision for it. It is well-known that stable neighborhoods of homeowners have far less crime and other social problems than those otherwise composed. Just wages, then, by promoting the dignity and independence of the worker, lead to greater stability and cohesion in society.”