I've found that by shopping at higher end grocery stores, or at least focusing on the organic/craft-oriented departments, the quantities tend to be smaller and much better suited to my childless, bachelor existence.
There was also a learning curve to preparing food for just myself to consume. The priorities are different from the family household I grew up in, so much of what I had learned didn't apply very well unmodified, to my adult life.
Families make the costly perishable ingredients go further by utilizing carbohydrates like pastas and breads as fillers.
I now make many of the same dishes I grew up eating, but without the pasta or bread, which I've entirely stopped purchasing to the very clear benefit of my health/weight.
When you dispense with the fillers, it's a lot easier to consume the perishable ingredients in one or two meals.
It definitely seemed strange at first to eat things like lentil or chicken soup or a meat ragu with pork ribs sans pasta or bread. But once acclimated, the recipes have changed a bit to be less liquidy while more meaty/beany with more veggies where applicable, and are very tasty and nutritious. It's basically decadence, and healthier than eating all the carbs.