notes里corporate finance部分讲股权回购的里面有一个example: eps after buyback=(total earnings-after tax cost of funds)/shares outstanding after buyback.

为什么只减去after-tax cost of funds，用来回购股权的本金不也是equity outflow么。虽然觉得书上是对的但怎么都想不明白。求助各位牛人指导指导