The comparison was between self-driving trucks vs drones, not human-driven trucks vs drones. Obviously those are going to be cheaper than whatever current technology we have.
And there's nothing preventing drones on the rough order of magnitude of trailers from flying around, as long as it's done in a safe and regulated way.
And there's nothing preventing drones on the rough order of magnitude of trailers from flying around, as long as it's done in a safe and regulated way.