You hear it all of the time, but I don’t think you realize it until you’re actually buying everything.  A few things that are expensive:

1. Diapers.  I knew we’d go through diapers, but this is ridiculous!  The kid loves to poop.  When he’s not pooping, he loves to pee.  Sometimes he really likes to do both at the same time.  Here’s the thing that drives a cheapskate like me crazy.  I go to change his diaper.  He’s peed it and there’s just a little poo.  You un-diaper him, clean him up, diaper him, and then pick him up with a big smile on your face knowing you baby is 100% clean.  As you lift him, you see his face contort and his stomach muscles contract and then WHAM… a huge toot… and a huge poop and you start everything all over again.  Money down the drain kiddo!  Next time, poop before the diaper change!
2. Wipes.  Same with diapers… the more you change the diapers, the more you wipe them clean.  You put the wipes in a box and pull them out one by one… they’re worth a few cents each and the batch of them is worth a lot more than that. 
3. Doctor’s visits.  After leaving the hospital (which I haven’t mentioned, but that entire birth process cost a lot), we had to go to the doctor three times for the jaundice issue.  We also have his 2 week appointment.  Each appointment, there’s a $25 co-pay.  Of course, that doesn’t even mention the actual cost of the appointment that insurance will not pay.
4. Formula.  We bought some formula when we supplemented to get rid of the jaundice.  That stuff is pricey.
5. College.  That’s going to cost a lot too.

In the end, it’s clear this baby will cost a lot.  I’m just glad we don’t have twins!