This is usually the point where someone interjects some examples of cheap foods that poor people ought to just buy - because everyone, everywhere has trivial access to their middle class shopping experience.
But even past that: Being poor also means subject to ceaseless Denial of Resources Attacks. Resources here meaning funds, attention, energy, ability, hope, will and anything one needs to raise one's station.
Hacking a meal plan struggles to rise to the top of a priority stack when one has dozens of problems in a critical state. And because of poverty, it requires 10x the steps to solve those issues than non-poor people face.
source: decade of hunger-level poverty with kids