In the 90s, I never set babysitting rates, and I don't think anyone ever asked me or proposed a rate, unless it was for a week or a summer. But I never wound up leaving a house with less than $40 for an evening, which was usually about 4 hours. I know I made less with family, but that's because sitting for family was supposed to be free, and they'd sometimes stick $20 in my purse here and there just to be nice.
Even then, it was hard to find a *good* sitter. I was a prize in the neighborhood. Everyone wanted to make sure I'd be willing to pick them over hanging out with my boyfriend. ;-)
I almost never hired a sitter for my own kids, because I just couldn't afford it. Once we moved away from family (when they were 7, 3, and 2), we pretty much stayed home until they got older. Somewhere in there, we could have afforded it once in a blue moon, but there weren't any reliable teens in the area. The one I was warming up to blew it when she told me how excited her boyfriend would be, because he loves playing with kids.
I did work daycare when my oldest was a toddler. It only payed around minimum wage (circa 2001ish) but it was a solid 40 hours a week, versus picking up a few hours here and there. Most of my coworkers did pick up additional hours from the daycare families at much higher rates for the irregular demand at premium hours.