I learned the economic stuff in Engineering school. I am a water resource engineering planner and we have to jump through all those hoops too.

Glen- my vinager bottle IS free because I have to buy the vinegar anyway. If it did not become my backpack bottle, it would go into the recycle garbage. You know, you can justify all your backpack food that way too- got to eat anyway. Hey- and a sleeping bag is a lot cheaper than a bed and you have to sleep anyway. If we go on we may be able to even say that backpacking SAVES money. Then we can get into opportunity cost!