“Fancy vegetables” aren’t expensive whatsoever. I’m not sure where this myth comes from that healthy food is expensive. It’s expensive at restaurants (you’ll notice even at something like McDonalds that a salad costs way more than a cheeseburger meal), but that’s only because they sell less of them & it’s marketed as a special “lifestyle product”.

Buying the ingredients yourself is dirt cheap. Have you ever shopped for yourself? Just go buy onions, broccoli, tomatoes, sweet potatoes, bell peppers, etc. - All of this stuff is ridiculously cheap. For simple dishes, try simply adding various vegetables to rice & beans with hot sauce. Or adding them to stir fry noodles with soy sauce.