airlines were not interested in voluntarily subsidising the costs of training navaids
No there's a joke! Airlines subsidising GA?
The reality is that airlines get a massive subsidies
from GA and the taxpayer.
How much does it cost to train a pilot from ab initio to airline standard? How much of that do airlines pay?
Every time a GA business puts money into training a pilot who's ultimate aim is the airlines, to replace someone else who has just left because they're working towards the airlines, that GA business is subsidising the airlines.
Every time a GA aircraft takes the long way around controlled airspace due to RPT aircraft, GA is subsidising airlines.
How much do Airservices/airlines pay in rent for the thousands of cubic miles of airspace they control access to? You can bet this has value to them, but they expect it from the taxpayer for free. What would Australia's controlled airspace look like if Airservices were required to pay rent per cubic mile?
I know that's the way the world works (and it's not necessarily a bad thing, granting CTA to Airservices for free maybe makes sense from a societal point of view), but don't bleat about airlines subsidising GA and expect me to take you seriously.
One thing to remember about "user pays" - it usually means that someone with money and influence has found a way to shift their costs to someone else. I prefer to refer to it as "loser pays".