Not to be snobby but I wouldn’t think that a typical family with an income in the 200’s would have an au pair.
That number as a median income usually indicates a well to do town. However, that’s median.
Think about it, there are towns where police officers earn solid 200’s. Do they have au pairs? Usually not.
I do have a buddy in Brookline MA whose kids’ kindergarten was in the mid 50’s. This is a different class of folks and yes they have au pairs. They are not too concerned about fast food service in decline