Diapers are expensive. You can save 30% on diapers, wipes, and other items on amazon.com and free two-day shipping.
When you register for Amazon Mom, you get 15% off select items (includes diapers). You can get an additional 15% with "subscribe and save" which means that you can schedule an item to be shipped to your house every month, 2 months, etc. No fees whatsoever. You can save tons on diapers.