I make ginormous amounts of homemade trail mix for about $15 and it is so easy!
The trick to making enormous quantities of trail mix for a relatively low price is shopping at Trader Joe's. They have the cheapest bags of nuts and dried fruits with the best selection. I like to go into the store and buy what strikes my fancy. Most often the cheapest and yummiest sounding items for me are the roasted peanuts, honey roasted peanuts (give the mix some sweetness), cashews, almonds, sunflower seeds and raisins.
I bring them home and mix them all up in my biggest mixing bowl. After they are all well mixed I store the mix in large ziploc bags. It costs less than $15 and is enough to fill two large bags.
This is the cheapest and easiest way I've found to make trail mix. I love that I control exactly what goes into my mix and I can keep it healthier.
