If the need is high and the budget low, we may choose the cheapest option. If there is very little difference in price, such as with organic beans and grains in bulk, we usually go with the more ethical choice. On of the key factors in living both frugally and ethically is doing with less . Often the items at the dollar stores are things we could live without. Small carboard boxes replace plastic bins, plain paper replaces coloring books and imagination replaces all those junky plastic toys and jewelry.
Organic food is difficult.
You can't really consume less food but you can simplify your diet. Instead of thinking you can't afford organic food because you can't buy the meat or milk, change your diet to include more of the organic food you can afford, like lentils and rice. We have tried to buy produce in season and through Farmer's Markets whenever possible. Another option is Community Supported Agriculture. People buy shares in a farm and then get whatever is ripe on a weekly basis.