I eat and grow all organic. No matter how dire my budget has been organic food has always been a big priority. I do understand that there are some people who really can't afford it, but to me sustainable, healthy food is way more important than new clothes, cell phones, movie rentals, or any other non-essential items people pay for. So often I hear the "organic is so expensive" argument from people who have way higher standards of living than I do, and it is frustrating. If you are buying from a reputable source, organic is more expensive because it represents the true cost of food, providing a livable income for the smaller grower, paying for that grower to practice sustainable growing to preserve our precious water and soil resources. Non-organic food is cheap because it is subsidized (USDA spends about $20 billion in direct subsidies for wheat, corn, soy and rice) below the true cost of production to keep cost low. In the US and worldwide, topsoil erosion, water depletion and pollution (non-organic ag is responsible for %70 of water pollution according to the EPA) are reaching critical levels. Of course with the fossil fuel issue food needs to be organic, local and in season. Either we pay the real cost of food now or our children will pay it on a global level.
On a practical level a great way to make organic food affordable is to cook from scratch, focus on whole foods (veggies, fruit, beans, grains, etc, not the store lol), avoid prepackaged foods, buy in bulk... Usually organic produce and bulk items are only a little higher in cost. I focus most of my meals around soups which are very cost effective. As a pp said, eating in season is a great way to keep costs down. And you can use the sun or your oven to dry foods, canning is cheap and easy, and you can fit lots in a standard freezer. You can also watch sales and look for near the pull-date specials to buy lots of soup meat to freeze, or milk to make yogurt. Often if you form a relationship with your store they will set aside produce that is fine but blemished so they can't sell it and give it to you for free. If you know what you are doing, dumpster diving is another no-cost option. I did it when I had no money. If you are willing to search for it, most communities have CSAs (community supported agriculture) where you pay for a box of veggies (some also do meat, eggs and milk as well) delivered week at very low cost. In my area you pay about $350 at the start of the season and get a huge produce box weekly for 5 months. That amounts to $60 a month! And many people share a "share" and cut their cost. If you are willing to search many farms are not certified organic but farm organically and have very reasonable produce. A good place to start is to find some Slow Food people in the area or farmers markets. Many small farms are open to volunteers and would trade a days worth of weeding or harvesting for food. There are also many people doing cow or goat shares as a way to get raw, grass-fed milk reasonably priced and locally. You can also order bulk items from places like Azure Standard or Mountain Peoples. Of course my favorite way to keep food cost down is to grow or raise you own. Dig up your yard and grow a garden, raise a few chickens for eggs, plant some edible landscaping. If you don't have the space there are many community gardens in urban areas and you can actually grow a lot of greens or herbs on a window sill. HTHs, people can be elitist about many things, but it doesn't always make them wrong about the core issue.
ETA- Yinsum-I think one of the reasons people judge others' food choices is because where are food comes from effects all of us, and our future. Of course some people just like being snobs.