What do you pay your occasional babysitters? Every lovely girl I've talked to about watching our twins has been very bashful about stating their rate. I'm getting a lot of "Oh, I don't have a set rate, whatever you think is fine by me". I want to make sure I'm paying them fairly - what's an average pay for sitters these days?

I plan on paying slightly higher given that we have twins, and also slightly higher for shorter time periods (when I only need a sitter for two hours or less) so that it's worth their time... but I'm still not sure what that should be exactly.

I realize it varies a lot by city, but would love to know what you are paying your hourly sitters!