I would expect between $2-$5 per employee touch-minute with automated baggage handling counting as a person to include the initial cost, the cost of maintaining it, and the cost of monitoring it. Figure about 10-15 touch-minutes per bag overall and that's as much as $20-$65 per average checked bag with some of that paid to run the airport.
I suppose one could look at air-shipping rates for similar weight and size to see what it costs without including the passenger. It may be a lower direct-cost for the passenger than the luggage, but the passenger is the one with the motive to get there and everyone one of them who doesn't board is paying the airline for a service it's not providing.