All this depends on his position, package and allocation: and which ones he wants to give you - there are a variety of staff concessionary tickets with different restrictions (firm or standby, firm with standby upgrade, the extent of the discount, some lounge access some none even if J/F).

The only constant is that if you are travelling on staff tickets you will be required to follow the staff travel rules (basically, don’t cause trouble and don’t project an unprofessional image). Even a firm staff ticket is liable to be offloaded (as are all revenue pax, but you’ll be off before them).

You’ll still have to pay taxes and fees though. If you are going to be on the most discounted fares, expect something around 90% off the full fare plus taxes.