暗扣

zhòng suǒ zhōu zhī wǒ guó jī piào jià gé yī zhí yǐ lái cún zài zhe àn zhé àn kòu de xiàn xiàng

众所周知，我国机票价格一直以来存在着暗折暗扣的现象。

It is known that there has been a phenomena of hidden discount in our airplane ticket price.