I find this question interesting, because I have been avoiding making my own almond milk. I assumed it was too expensive. Looking closer at it, the cost may be about equal, and it's fairly quick and easy.
For reference, the box of almond milk I have in my refrigerator (Blue Diamond brand, not organic) contains the following: purified water, almonds, tapioca starch, calcium carbonate, sea salt, potassium citrate, carrageenan, soy lecithin, vitamin A palmitate, vitamin D2, d-alpha-tocopherol (natural vitamin E).
Homemade would have just almonds and water, and maybe a little vanilla bean, if you like the flavor.
I may try to make my own this weekend.