I guess I'm getting off cheap and never realized it! Our evening sitter charges us $3/hour total for 2 kids, ages 5 and 3. However, when we figure up the nightly rate, sometimes we throw in an extra $5 or so dollars onto the total to round it up. She lives across the street and is from a very very good family. She became certified in CPR and first aid when she was 13, and we started using her after Mom suggested it at a garage sale. She's 15 now. She's always been available when we need her. The kids love her and she's fun for them to play with. She's a straight A student, not that it matters, but I've had other babysitters before her, and it seems the smarter they are, the more reliable and better caretakers they are as well.
We had a girl before her who charged about the same....the only problem was once she got her driver's license, she became unreliable and too tired to babysit. I remember one time we needed her during christmas break for a day while we worked. When she got to our house, she said she hadn't slept all night, having been up with her friends. Another time, she forgot, and her Mom had to track her down. Needless to say, we stopped using her after those 2 incidences. But, our sitter now is absolutely wonderful, and I get nervous just thinking about her 16th birthday wondering if she too will "change".