One day, a magician came to the man and said to him, "I can make your son happy and turn his frowns into smiles, but you must pay me a great price for telling him the secret."

一天，一个魔术师来到这个人跟前，对他说：“我可以让你的儿子高兴，让他一展愁眉露出微笑，但你必须为告诉他这个秘密付出巨大代价。”

youdao

You must pay careful attention when doing accounts. You're likely to make errors if you're not careful.

算账得专心，一不留意就爱出错。

《新英汉大辞典》

You must pay attention to your teacher in the class.

上课的时候必须专心听老师讲课。

youdao

You must pay the bribes that you must and tolerate corruption from top to bottom.

FORBES: Leading Economist Gives Up On Putin's Russia

You must pay the tax you owe, and we will make sure you do.

BBC: Danny Alexander

We might go further too: you must pay a tax to landfill material these days.

FORBES: Despite NPR, No, Burning Trash Is Not Profitable