Most newborns average over 3,000 diapers each year. With one baby in the house, expect to pay anywhere from $40 to $80 per month on diapers, depending on the brand (generic, organic, etc...). A good price per diaper is around $0.20 or less. The cheapest place to buy diapers is generally Amazon, but you can find other sites with deals as well. For example, Amazon recently launched their Mama Bear line here which significantly undercuts other name-brand diapers.