We have to do what they say because they're the ones who are paying the piper.我们必须按他们说的做，因为出钱的是他们。

You know what they say: he who pays the piper calls the tune. [=the person who pays for something controls how it is done]你知道人们所说的：谁付钱谁做主。

They have mismanaged the company for years, and now they have to pay the piper.多年来他们把公司经营得一团糟，现在不得不承担后果。