The player is certainly "worth" 1.3 million in the same way a rolex is "worth" 5k. As in, that is the going rate for the player/watch. He could train him or sell him right back and quickly recover his spent money. However,everyone is arguing that the player is not actually bringing 1.3 million worth of benefit to his team and I would agree with that.
Rebounding, like most skills in this game, are by comparison against the player they are up against. In Div. IV, it is rare to see a prolific rebounder even. That means diminishing returns for every pop beyond that point, unless you plan on selling the player or using him at a higher level (which are both valid options in this scenario). Those extra pops, for which you are paying dearly for, would much better be spent on IS or ID. My 18 year old PF would outplay this player.
I also think a few people (or possibly me) in this thread have a misconception about rebounding. It is my understanding that the rebound comes down to a matchup - a randomly chosen offensive player vs. counterpart. This player will certainly win almost all of the rebounding battles, but so would a prolific rebounder. Just because he is a Prodigious rebounder doesn't mean he gets more opportunities to rebound, just that he will win more of said opportunities. As an example:
30 opportunities for PF rebounds in a particular game:
Prodigious (25) vs. Strong (5)
Prolific (23) vs. Strong (7)
These are made up numbers, of course, used to paint a picture of the concept I am trying to describe.