A box of cereal is like $6 and all sugar. It will provide 3-4 bowls of cereal for that price, with no actual nutrition. If you can afford a box of cereal a day, you can live on instant noodles instead for like 3 days and have the 20 for a brand new rice cooker. Or just go to the thrift store.
Cereal is not a poor person food. It is not nutritious, cheap, or filling. It is an expensive box of sugar. I get that it can be hard to imagine conditions we haven't personally experienced, but it can't be THAT hard to do basic math and put yourself in that situation for one second to understand that eating cereal for every meal is not cheap or sustainable.
At what cost?