Article says their recurring cost is $17.5k, they'll spend at least that amount in terms of human time tending to their cluster if they have to drive to it. It's also a question of magnitudes, going from $0.5m/mo to $0.05m/mo (hard costs plus the extra headaches of dealing with cluster) is an order of magnitude, even if you could cut another order of magnitude it wouldn't be as impactful.