I imagine estate tax revenue would increase more than tenfold if the rate were cut to something like 7 or 10 percent. As it stands, the estate tax collects less than $20 billion or so. This is a pretty paltry sum for a provision that has such an effect on how people do various things. The purpose is clearly not to raise revenue. It is just a massive subsidy for lawyers and the rapidly growing non-profit / foundation sector.