system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5:why does it cost more to make your own trail mix ?

If you buy a bag of trail mix, it may cost you about $7-$10 without any expensive items (e.g macadamia nuts). If I tired to make the same serving, but buying the ingredients separately (e.g. 1 bag of peanuts, 1 bag of m & ms, 1 bag of dried fruit) ends up being 3X the price , even if I buy in bulk to make multiple servings. Why doesn't it work like buying a sandwich? Buying a sandwich cost about 5 bucks, but you can buy bread, lettuce, mayo, etc. and the cost comes out to about $1 -$3 bucks. Same thing with hamburgers, hot dogs, pretty much any meal or snack except trail mix. Why doesn't this apply to trail mix?
gpt
I would assume that it's because the companies will buy the ingredients in bulk, whereas you buy smaller quantities. It normally costs far less per amount (say, 20g of macadamia nuts) if you buy a huge bag (and then split it into smaller portions) than if you buy a small bag. Therefore, the costs of making the trail mix are less so they can sell it to you for less.

Same concept as when you buy a single pack of crisps or a multipack. The multipack will cost less per pack of crisps than your individual single pack would cost you.