Nannies are more expensive ($10 - $15 per hour). If you want to get a sense of going rates, check out www.sittercity.com.
Daycares can run you $1000 - $2000 per month, depending where you look. Average is about $1500 I think.
As an experienced nanny, I generally charge about 15/hr. That's about 2400/mo fulltime. I think a nanny is reasonable for most persons when they are working part-time (as I am) as it costs less money, but is way nicer (and more comfortable for the kid) than a daycare facility.
Sittercity is a great site, I've found many of my jobs on there, including my current one.