Below please find a calculator for cloth diapering. It is customized so you can put in values that work for you. Here are some estimates you can use to help you:
Prefolds can be about $2 each
All in ones and Pockets $17
Imported pockets from China $9
Disposables .25 (at grocery store), .17 at Costco, .11 with avid couponing
Your baby is expected to use about 10 diapers/day.
I also get a lot of my diapers for free using Swagbucks (and my cousin does this for disposables as well).
You can also buy/sell used (click here for more info)
(confused by the lingo? Go here)