It's certainly open to debate, but I'm questioning that the delivery itself is compensation enough for everything that Google is receiving from the testers. Obviously Google (and you) thinks this, but I don't agree that there's only one possible value-based assessment of the relationship.
But your characterization of it I found disingenuous: "Am I to think of Google as just another buddy who needs a lift to the bus station?"
There's no reason for the snark, and to pretend like Google is just trying to score a freebie like your hypothetical mooching friend is framing the argument disingenuously. The cost of delivering something same-day is non-trivial - Google is not expecting a freebie, though you are of course welcome to value your privacy above that dollar amount.
EDIT: Fixed typo