How much is too much money for babysitting!?

I am watching a 13 month old girl. Her mom works 60 hours a week and I am getting paid $60 a week. Unless she has someone else watch her then she subtracts out the difference. I provide 3 meals and 2 snacks. She provides milk. I feel like I am getting taken advantage of! I want to ask for more money but I don't want to sound unaffordable. Its 12 hour days. She drops her off at 7 and picks her up at 7. Mon-Fri. What do you think a reasonable price would be? Thanks for your help! =]