kànqīng zhǔcài yǐnliào zhǔshí pèicài néng bu néng huàn cái zhīdào huá bu huásuàn

看清主菜、饮料、主食、配菜能不能换，才知道划不划算。

You'll only know if it's a good deal after checking whether you can swap the main dishes, drinks, staple foods, and side dishes.