A couple of corrections there sf17 fisherman. There can be no donation in these cases that are tax deductible as they are purely "Fee for Service" no matter how you might want to dress it up'
If you want to avoid paying towing fees join your local VMR group and you will get no charge or little charge. If you called out the RACQ if your car broke down and you wern't a member it will just be a matter of get out the cheque book or credit card.
Emergencies like you quoted will cause activation of the police who will activate the VMR group and their activation will be covered by the police.
The VMR money doesn't grow on trees and the subsidy from the government for running cost is poor so then the orginisations have to fund raise and have membership fees to pay for the difference. There would be no way a commercial operation could compete with volunteers on a cost basis.
VMR groups have now been banned from carrying fuel other than in their vessel fuel tanks so if you run out of fuel you have only one choice from VMR and that is a tow.
Another thing I have been recently made aware of that Marine safety board in QLD are now taking a hard line approach to incidents and with the example you gave you could possibly end up in court defending your actions.
Go down to your local VMR and get a membership form and be a member treat it the same a RACQ membership. If you can afford the boat you can afford the membership it is cheap insurance.