Just enjoyed a city-int'l airport trip on opal today for the princely sum of $3.10 today. To work out how, combine tapping on with 'minimum fare' value on cards, with principles learned on this site for Brisbane's Go Card (specifically airport to GC train)...
How much does an unregistered Opal card cost? How about the minimum opening balance?
I seem to recall something similar in Vic for the Myki cards....