Optimising for economic cost with the only requirement being "fill your belly" and "be palatable enough", tends to result in poor nutrition. This is roughly how the industry optimises food - minimise economic cost, maximise yield, and maximise sales (make everything artificially hyper palatable), with terrible results.
In the long term this is partly covered by the economic cost on a personal basis because of the cost in health care and loss of ability to produce income due to deteriorating health. But this is displaced in time, and you do not want to do this experiment on yourself, it's not reversible.
Calories are not equal, as a general rule, buying cheap food often means cheaping out on nutritional value. If you want to frame it in terms of money, buying good quality food now is an investment in your future.