Over 100k. We've lived a privileged life. I've been a SAHM since my first was born but have always had passive forms of income, ie rental properties, horse boarding, investments.
Most AP parents I've known are well-to-do. I think the stereotype has a good bit of truth to it. Personally I think it's more because AP parents (in my experience and because it makes logical sense) are more likely to be higher income because they are more likely to be educated, and I think educated people are more likely to AP.
Educated parents are more likely to breastfeed; more likely to choose organic/healthier food; less likely to use corporal punishment, and I'm sure a variety of other practices that jive with AP/natural living.