I think that where one stands on this is determined by one's understanding of review scores. If a review score is supposed to represent the quality of a game, then it's absurd to allow price to affect it. However, if a review score is supposed to represent the value of a game, then it makes perfect sense.
I tend to agree that price matters - a review score is primarily a tool used by owners of a system to determine what they ought to buy, and is only secondarily a way to directly compare games on/across platforms.
Look at reviews of other products. Any iPhone review that doesn't consider the price a negative is being silly, any Wii review that doesn't count the thing's affordability as a bonus is being dishonest, etc.
Most people don't read reviews in order to have arguments about which game is better - they read reviews in order to see what's worth buying, and it's no sin for a reviewer to consider all factors that determine a game's value. Considering the price of the game yields a score that is more useful to the average reader, which is exactly what they should be trying to do.
Edit: And while I agree that Warhawk isn't quite the same thing as a $10 XBLA game, the precedent still exists. Cheaper games are not held to the same standards.
Instead of thinking of this as 1up penalizing the game for costing more than $30, think of it as giving the game a handicap if it's $30 or less.
