Hi K.,
50 cents for a diaper?! OUCH! I am always on the lookout for bargains and never pay full price. For infants, I loved the Pampers Swaddlers and always bought them when they were on sale and when I had great coupons so I always saved a good deal of $$. I stocked up way before I gave birth to my last two babies. As my babies got older (I have three kids and my youngest is now 6 1/2 mo old), I use Luvs diapers and always had great success with them (I heard somewhere that Pampers actually makes the Luvs diapers but I haven't confirmed that yet). I buy them in the bulk box at HEB or Target, and again, I buy them when they are on sale and when I have coupons. When I do find diapers on sale, I buy lots of them - the current size plus the next size since I know the baby is going to grow up. :>)
As for how many diapers a kid goes through in a day, it really depends on how much they are eating, what their movements are like, etc.
I haven't used the store brands diapers so I can't give you an opinion on those. Personally, I can get diapers for less than 20 cents each and I know you can too. :>)
If you do buy a drugstore brand diaper and they don't work out, just call the customer service phone # on the package and tell them (tactfully of course) why those diapers didn't work out. They will usually compensate you somehow with coupons, refund, etc.
Hope this helps!
K.