I would assume it's because the bigger the diaper, the more stuff they use to make them. Therefore, you get a fewer number of diapers for you money, but the same amount of "stuff." (has a bad case of mommy-brain and can't think of a better word than stuff...sorry)
I'm assuming it's the same reason that the person who has to by 2XL pays extra...require more "material" to make them. I hate it too. Mostly because my DD can wear size 2, but I can't ever find them so I end up with size 3, and less of them!
Re: Diapers: the larger you go the less you get? Why?
Breleigh & Mason
Ditto this. Newborn diapers come like 200/pack - if you had 200 size 4 diapers the box would be so big as to be impractical.
DS1 born June 2008 | m/c at 9w March 2011 | DS2 born April 2012