These are indeed multipliers for the price of items in each category. The only reason for using powers of two was to allow easier division (16/128 instead of 12.5/100 for increments of one eighth) and get nice rational numbers out of it when re-multiplied with the skill level factors from distribution.ini. It's more or less an aesthetic choice
The game price of an item is COST * (category SCOR)/128 * (nebula SCRN) / 128 * (enemies SCRE) / 128