"Among voters earning less than $100,000 (78 percent of voters), 55 percent said they voted Democratic, 43 percent Republican. Among those earning $100,000 or more, 47 percent voted Democratic and 52 percent Republican."[0]
It's possible that the specific threshold chosen creates two artificial groupings which happen to have different partisan ratios, but if a similar trick can be done by splitting the population into three groupings then I'd be interested to see those numbers.
[0] https://www.minnpost.com/health/2007/11/party-rich-democrats...