I don't even know how BBPro calculates VORP. If anyone cares to point me in the right direction, that would be good.
The Game Guide offers a short (and somewhat hazy) explanation. Replacement level for hitting is determined by 80% (or so, depending on the player's position) of the league average runs per out. Replacement level for pitching is 1 run over the league average (per 9 innings, presumably). Everything is normalized for park effects and position. Beyond that... beats me.
Also, VORP is measured in runs (
AFAIK), so at least there's a real, meaningful unit of measure associated with it.