All perfect praise be to Allah, the Lord of the worlds. I testify that there is none worthy of worship except Allah and that Muhammad
is His slave and Messenger.
You have mentioned that everyone is aware of this arrangement and agrees to it. Given that, there is no harm in the practice you described, and one worker's dislike of the wage (1000 KRW) does not affect this, as long as he has consented to it — for the consideration lies in his agreement, not in his dislike of the wage or his hope for more than it.
What is apparent from the context of the question is that the contract between you and the company is a contracting agreement (aqd muqawalah), which is, in principle, a permissible contract.
It is stated in a resolution of the Islamic Fiqh Academy: "A contracting agreement (aqd muqawalah) is a contract by which one of the two parties undertakes to make something or perform a work in exchange for a payment that the other party undertakes [to pay]. It is a permissible contract, whether the contractor provides both the labor and the material – which jurists call istisna' – or provides only the labor, which jurists call ijarah 'ala al-'amal (hiring for work)..." [End of quote]
Likewise, if you were an employee of the company managing the workers, and you agreed with the company that your wage would be one thousand, while it pays the workers five thousand, this transaction is permissible with no issue in it.
Allah Knows best