Is this really a comparative analysis of how much it costs to make games across systems, or is this simply an average cost across all games released? I'm thinking it's the latter, and that would not be much of a surprise. PS2 has an awful lot of games from a vast array of publishers. I would imagine quite a few of them have low production values and thus cost little to make. I'm sure such games, were there a market for them, could get made for the Cube. Those games would drop the average cost for PS2 games.
Basically, a meaningless stat if that's what we're talking about here.