It's not open to negotiation, there is a standard amount plus add-ons for spouse and children. I don't want to post the amount here as it is confidential but it is enough to get a decent apartment with facilities (pool, tennis courts etc) near the school. You will be told the exact amount if they offer you a contract.
Yes, there is a standard amount depending on applicant circumstances, but it is negotiable (slightly). I worked there previously, left 5 years ago.
That said, maybe the policy has changed.
Regardless, seems odd if the OP expected posters here to publish amounts paid to UWC teachers.