"Our luxuries are our children's necessities"...? What does this mean?

To answer this question, we have to first define our terms. Necessities are things that people need to remain alive and healthy regardless of their income. For instance, everyone requires food, housing, and whatever essential goods or services contribute to their health. Luxuries, on the other hand, are unnecessary items that are ornamental, expensive, or difficult to obtain. Income elasticity of demand is an economic term that defines the difference between necessities and luxuries. In a basic sense, necessities are things that everyone at all levels of income buy, while luxuries are measured in terms of demand as a person's income rises.

However, in a broader sense, necessities depend not only on what's affordable, but also on what's normal within a certain social group. What becomes a luxury or a necessity between generations also has to do with some goods becoming obsolete and other goods entering the market. Research shows that these values are not constant, but rather they change over time.

To get back to the question, "our luxuries," meaning whatever parents considered luxuries in the past, may have included items such as cell phones and computers with internet, because these goods were either nonexistent or too expensive for most households. However, nowadays, these are necessities for many children. They need cell phones to keep in touch with their parents and friends; many households don't even have landlines anymore because each member carries a cell phone. Many students also need computers with internet to be able to access their homework assignments and turn them in. These are a few of the numerous examples of how luxuries for parents become necessities for children.
https://www.investopedia.com/terms/i/incomeelasticityofdemand.asp

https://www.moneycrashers.com/difference-between-needs-wants-luxuries/