Your cost per station is wildly undervaluing things, since you are not taking into account shipping, installation, training, verification, auditing, disaster recovery planning, etc, etc.
Forgetting the exact cost, Apple has enough cash to give retailers an incentive and may have already done that with those that are already onboard. Note I said "incentive" not "paid for everything". This wouldn't be something that they would necessarily disclose either, for obvious reasons.