I am south of Boston. We hired our nanny at $10 and now she makes $13. She gets 2 weeks paid vacation (weeks of our choosing) 5-paid sick/personal days, paid major holidays (the same ones I get) and one week pay "holiday" bonus. The cost was (is) not much more than daycare centers in this area. Its the other expenses I didn't take into consideration meaning that my oil and water bills were so much higher since there was someone in the house all day plus added groceries etc. DUH!! I hadn't budgeted for those so take that in to consideration.
To me the most important factor was allowing my son to be on his own his own schedule not someone else's. If he needed to sleep till nine am he could. If he was hungry he would be fed right away not have to wait for someone with free arms. If he was crying someone could hold him and not have to have the attention divided.
Plus I am a natural stress ball. Knowing that I didn't have to rush around every am trying to get out the door on time and then rushing around at night getting everything organized for the next day was a huge bonus. Also being able to still got work when my son was 'sick' (temp at hundred which most daycares don't allow but otherwise fine, obviously not really ill!!) and having someone to help out when I am sick enough to stay home is a real bonus. I get paid sick time but husband doesn't so if we both had to stay home it would be a loss of income. Plus she is responsible for my son's laundry, dishes, keeping his toy area neat and clean, changing area stocked etc. Another time saver and stress reliever!
Here is a link to the International Nanny Association salary survey. Its kind of vague but it gives you an idea. At $13.00 an hour I am smack dab in the middle of the Boston range. http://www.nanny.org/INA_Salary_Survey2.pdf
Oh and by the way I used an agency, which added another expense, but they do all the background checks for you (criminal, driving, etc). We have had our nanny for almost 3 years now but the agency continues to be helpful. My nanny has been out for the past 2 weeks for medical reasons and the agency had 3 people for me to interview for short-term coverage the next day.