I seriously doubt that collecting ballots eats up the $650,000 to $2,000,000 a year that this would cost. If this becomes reality, how many extra trips will people take to the Post Office? Leaving mail in a curbside box isn't secure, there aren't as many mail drop boxes as there used to be. If having free postage is the motivation for me to vote, it'll require a special trip to the Post Office.
Will the state be including pens with the ballots too, to make it that much easier to vote?