Why does everything at the grocery store cost about $5 regardless of whether the ingredient is actually expensive to produce

A single mango at Kroger? $4.50

Small bag of rice? $3.75

Larger bag of rice? $5.50

Cheese is somehow more expensive than beef per pound, both being around $5/pound

Historically cheaper meats are around $5/pound as well despite definitely being less expensive to farm

Is there an online store or some other place I should be getting my groceries? The grocery monopoly is making it hard to afford to live. I'm about to start eating animal food since it costs less than $5/pound