How many diapers do babies go through?

Any guesses how many diapers babies will go through?  I saw these numbers from Babies R Us and I was shocked, especially since my numbers are very different from these so far.

Newborn/Size 1 (NB up to 10 lbs, Size 1 up to 14 lbs) = 320 diapers
Size 2 (up to 18 lbs) = 870 diapers
Size 3 (up to 28 lbs) = 870 diapers
Size 4 (usually used until potty trained) =728 diapers

Owen will be 5 months in a week and we are still on Size 1.  We've gone through at least 3 or 4 boxes of the 200 packs so far ( including Newborns) but our little niece started Size 1 diapers during her first month so they didn't really use Newborn sizes.  

I was telling my friend the best way to buy diapers is to do it in advance. That's what we did and I'm so glad because we've maybe bought a box of diapers and wipes since he's been born.  I told her that you get three free months with the Amazon Mom Program (through Amazon where you can save an additional 20% on diapers and wipes).  A monthly program is like $80 but about four months before Owen was due, we signed up and used the three free months to stock up on diapers which are already a discounted deal at Amazon, and then with the 20% I was saving I think $50 on my purchase a month.  I loved having the diapers available in my closet and bought up to a Size 2.  I definitely bought more Size 1 diapers then needed but am glad that we haven't had to run to the store in the middle of the night or pay for a lot of things for him recently which is nice.  

The first two months he was so expensive with buying things we didn't know we needed or wanted and so buying diapers ahead of time was an awesome plan.  So first time moms, I totally recommend buying diapers a few months out to save money and spread out how much you are spending because, believe it or not, babies can be expensive!