>> OTOH since the price is given for the lower payload which covers all/most the cost of the hardware, one may be a bit angry if the price per kg doesn't drop a

>> OTOH since the price is given for the lower payload which covers all/most the cost of the hardware, one may be a bit angry if the price per kg doesn't drop a lot after that. That's not necessarily true. The Falcon 9 has the potential to be reused, but requires additional fuel reserves in order to handle the return procedure. I'm not certain, but it's possible that a full 21t payload wouldn't allow for that additional fuel capacity and therefore your single launch would have to account for the entire cost of the rocket, whereas smaller payloads would be able to spread the cost of the rocket across multiple launches.