I never buy the specialised backpacker meals. Not only are they way too expensive, their sizing is wrong too and they are too heavy and bulky for the calories they offer. Many of them are in the 700 kcal range, so that is not enough. You would need two packs for a meal. On the other hand, if I get two Batchelors (or similar) "Pasta & Sauce" packs in the supermarket at £0.50 each, this approaches 1000kcal, which I consider the minimum for a meal. These two are still smaller and way cheaper than backpackers meals. Unfortunately, they have recently decreased the sizes from 120g to 99g, so often I mix in some extra dry pasta to get above 1000kcal. I'm also adding extra salt when it is hot.
In other countries they have similar meals at low prices. Knorr Sides in the USA, I used Woolworths own brand in Australia, etc.
For breakfast and snacking I just use a trailmix of peanuts, raisins and most important: chocolate! That ingredient is important because it keeps you eating and you don't get bored of it. M&M's are great for that because they handle the heat quite well, as long as you don't crush them. Sometimes almonds, sunflower seeds, etc too. Especially in America they sell excellent trailmixes with delicious ingredients. One of my favourites had almonds, raspberries, white chocolate and black chocolate. Yummie!
One of the things I learnt is that on long distance walks your body just wants the calories and the salts. Therefore, stuff that you wouldn't touch at home tastes delicious on the trail! On the PCT I lived for 5 months on just Knorr Sides, trail mix and vitamine pills. I never got bored and never got sick! After the first 1000 miles I was eating 5000 kcal per day. That's a lot of food to carry, but it is what your body needs when it adjusts to walking all day. However, in the first ~3 weeks you can still get away with half that amount. On my WHW + Cape Wrath Trail walk (3 weeks) last year I lived on just 2750 kcal per day and that was still fine, but had it been longer then hunger and weakness would start to set in. On the Larapinta (Australia) last year I was eating 2600 kcal/ day for this 12 day walk. I could get away with so little because it was the first walk of my trip and that was good because I didn't resupply so I had to carry 13 days food from the start (I always carry 1 day extra for flexibility). But with the food I had this was only 573 gram per day (Batchelors Pasta&Sauce + trailmix, about £3 for an entire day worth of food)