Hi Pedota,
I can't deny that staff travel is a benefit. But I can assure you it is not all it's cracked up to be by those that don't understand it.
Staff travel is "space available". Meaning, if there isn't a seat available you wait for the next flight which may be anything between a half hour to a week later. This means that trips usually can't be planned until the day before travel in order to pick a flight with spare seats. Even then you may pick a flight with 20 spare seats only to find out 15 minutes before departure that, due to additional freight, you miss out.
Staff travelers also pay, on top of all applicable taxes and fuel surcharges, a percentage of the FULL FARE which is usually significantly higher than the DISCOUNTED FARE that most punters pay these days. DOUBLE this if you want an upgrade... subject to availability. This is allot more than nothing, which is what the airline gets if they upgrade pax.
As for the economics. Have a think about this. If you were driving from Sydney to Perth in 50 seat bus with 49 people on board how much more do you think it would cost you to carry that extra passenger? By the way you only have to feed him if there's something left after everyone else has been served.
If it makes economic sense to you to leave seats empty for the the comfort of commercial pax, as you suggest, then I want some of what your smoking...
Where you get the idea that commercial pax "subsidise" staff travelers is beyond me...
regards, JA1