Direct relatives of eligible staff (spouse, brother, children etc) get the heaviest discounts, referred to as ID90, where a single sector could be as low as 10-20$ + taxes. However these are standby, not confirmed. On the other hand a Cat C ticket (also called "wider eligibility") can be issued to a much broader category of people, but isn't much of a discount over revenue fares unless you need a one-way. Think 130$ + taxes or so for a mid-distance flight (I don't have the table in front of me right now so going off memory). Pricing is per segment, so obviously this type of ticket lends itself to one-way ticketing.