One gallon, there is no cheap replacement. Have you tried Organic Silk Vanilla (or another flavor) Soymilk? I think Silk is the brand. It is grittier, but works with cereal and is great with fruit smoothies.
Are you lactose intolerant? There is a lactose free milk (also expensive and not so great tasting).
Plan for the worst, hope for the best, and expect something in between. -RTW
If you had …one shot…one opportunity to seize everything you ever wanted, one moment, would you capture it, or just let slip.