I am a nanny. I make WAY over $3.00 a hour.
What parents pay for in a nanny is the fact that they don't have to transport their child(ren), the nanny comes to them. The nanny provides light housekeeping. The nanny provides one on one (depending on the number of children) care. The nanny provides personalized and individual care not only for the child(ren) but for the family. You don't get this within daycare or home care.
When I read ads like this, I find it insulting. A few times I have emailed these people and told them Good Luck! I truly believe you get what you pay for. So if you want Mary Poppins, then you need to pay more than $3 a hour.