The thing about food…at some point, you get what you pay for. Sure there are healthy, cheap dry goods like beans/lentils/brown rice, but in general the healthier you eat the more you pay. $400/mo is a good budget for 2 people eating a whole foods, unprocessed diet and eating in almost every meal. If you wanted to swap in pasta and ramen a few nights a week, your costs would reduce but so would your health in the long term.
Generally, my recommendation with food is to go pastured/humane certified/organic/etc on the animal products and don’t worry too much about the produce. We splurge on higher quality dairy and eggs because pasture raised animal products tend to be far more humane and environmentally sustainable, and they are also higher in omega 3s than caged/100% grain fed animal foods. Most of us could use more healthy fats in our diets, particularly the omega 3s, so if you have the money, pastured animal products can be worth it.
For produce, I try to buy local and seasonal before organic, as local/seasonal is more likely to be fresher and have retained more nutrients than any produce (organic or not) that spent days or weeks traveling to my grocery store from across the country or planet. It also has the added benefit of supporting our local farmers and ensuring that small farms stay in business. The only scientifically proven benefit of organic label produce is lower exposure to certain pesticide residues in the short term, but there is absolutely no mainstream scientific evidence to show that eating a diet high in organic labeled foods prevents cancer or other diseases. So basically, yes eating organic does reduce (but not eliminate) your exposure to certain classes of pesticides, but we have no available evidence as of yet to say if that matters at all. The only evidence linking pesticide exposure to poor health tends to be in populations that are exposed to extremely high doses for long periods of time, like agricultural workers or people who live right next to farmland that is routinely sprayed. The public takes these findings and extrapolates it to their own circumstances, thinking that if large amounts of pesticides are toxic, then even extremely small amounts must also be very toxic and must be avoided religiously. There is a massive difference between getting covered in this stuff or breathing it in, and picking up extremely small trace amounts that are left over.
If you are anxious about conventional produce, focus your organic dollars on the dirty dozen (foods that tend to have higher pesticide residues than others) or those foods that aren’t protected by an inedible peel (ex: buy berries and salad greens organic, but avocados and bananas conventional). Wash your food, and forget about it. Seriously, there are so many bigger concerns out there in terms of exposures - like drinking water quality, lead, etc. I find it silly when people insist on eating only organic but have never had their tap water tested in their old homes for lead, copper, etc. Lead has been shown to severely damage children's brains, and yet too many people choose to freak out instead over trace amounts of pesticides that have never been shown to directly hurt anyone.
For someone who doesn’t have the extra cash to just blow on the questionable returns associated with organic label foods, I would not be splurging on a ton of organics given the current state of the evidence.