I think a lot of it depends on your area and the going rate there. A more rural area would not pay what the "city area" pays.
That said.... our daughter turns 16 on 12/27 and she has been babysitting since she was about late 14. She babysits a LOT more now and regularly with 3 families who live in walking distance from us, 2 of which have 3 children each and 1 with just 1 child.
The cheapest family she will only babysit for if she needs money has 3 girls under 9 that are pure hellions. They offer her $5/child/hour. She is rarely available to them, NOT because of $$... because they are wild. She said she'd rather take on a house full of boy children vs these 3 girls.
She is routinely paid in CASH and she gets anywhere from $12-15/hr....sometimes $10/hr.
When we used sitters, we guaranteed $40 for the night CASH and if we cancelled for any reason, we paid her the $40 because she saved the night for us. I now realize the importance of that because my daughter saves the night for families and turns others down when she is booked.
On top of the $40, we added $10/hr. Our weekly date nights were routinely $60-$80 cash. A small price to pay to have special couple time.........WHICH IS PRIORITY for us as a couple.....not DESPERATION. Something must have worked.....we're going on 22 married yrs, 25 together this New Years Eve.
GOOD sitters save their nights for the families who pay well and have better behaved children.
Good luck... it is easy money, especially for a 15 yr old.
EDIT: My daughter is CPR trained, black belt and she has never set a rate. She has received the jobs she has based on referrals from families who have used her as a sitter. She accepts what the person hiring her offers.........NOT taking advantage of someone. She has a lot more class, morals and ethics than that, wealthy county or not.