I'm really not sure. I know for Hopscotch (similar to WeeWatch) in my area charge parents $42/day (FT infant). The Provider gets $35 and still has to pay her expenses out of the remainder. So, a 20% loss for that one, less expenses. Andrew Fleck charges the parent $48 and the provider gets $35 - approximately 28%. So they can vary anywhere from 10%-30% depending on the agency. There are several Weewatch infant spaces in my area that charge the parents $42, so I would assume t amount held back from providers would be similar. These are the lowest priced spaces in the whole area and have been sitting there for several months. I think that speaks to the agency's quality. And for some areas (like mine), those agencies are all that's available. And then there is Compass, that offers a $100/mo package, which is basically a 'no frills' kind of deal.
But really, we (CICPO) are of the mind that we shouldn't have to fishing around for the best of the poor options out there.