If you truly understand that $500 is the non-refundable application fee, then why did you write "500元已被沒收"?
Debbieip explained very clearly that "那是報名費,不是留位費,所以不會退回,所有國際學校都係收十分高的不退回報名費的。" If you can't handle losing that $500, you should not have applied for the school in the first place.