And the first possession of the game counts for as many points as the last.
Believe it or not, that isn't true.
Not all games are decided by a single point. If the game is decided by a wider margin, then each possession counts that much less: A team that wins 120-100 would still have won even if they had gotten value out of only 90% of the possessions that they did.
When a game is starting, there's no way to know how close the final score will be. So to accurately assess how much the first possession counts, you'd have to weigh it by the range of all possible score spread outcomes. Statistically, then, first possessions are devalued by those cases in which the eventual score margin is large.
For final possessions, there is much less uncertainty about how much it counts. Of course if the game is a blowout, it makes no difference at all what happens in the last 30 seconds of garbage time. So final possessions are not more valuable
in general than opening ones, but in games that prove to be close, the known value of a final possession
as it is happening is greater than the projected value that the opening possession had in the same game.