score:3
I don't know where you got the "single visit" thing from? An eVisitor can be used for as many visits as you like during its validity, only you cannot stay longer than 3 months each time.
As stated here (click on "What the eVisitor lets you do"):
enter Australia for up to three months during each visit during the 12 months from the date the eVisitor is granted
So your question is void: there's no reason for a German to pay for an ETA rather than getting an eVisitor.
But in any case: when you clear immigration in Australia, you've entered/left the country, period.