As N and I prepare to do the JMT, we've been dehydrating our own fruits, veggies, and meats to make our loads as light as possible for as cheaply as possible. It takes forever, but it's much more fun (at least for me) and healthy to pack one's own meals rather than use store-bought packs. Almost everything I'm packing just needs to be boiled or soaked in water and it's good to go.
We're planning on mailing half of our food to a midway point along the trail; they'll hold it for a small fee. On average, these meals still cost more than our usual meals as they contain much more meat and have bigger portions, but I think we've kept costs down pretty well.