"At bats" are actually "Plate Appearances" (since most people don't know the difference and "At Bats" is shorter, and seems to make sense to the most people)
Team total payrolls are estimates and do not fully reflect prorations due to player trades, obligations to traded players or contract bonuses.
Cost vs. performance score is calculated as ((MLB Average Salary/Player Salary) * Player WAR). For negative WAR it is: ((Player Salary/MLB Average Salary) * Player WAR)
Team Cost vs. performance score is calculated as (Player's Percent of Team WAR/Player's Percent of Total Team Payroll).
Figures for all non-baseball related facts have been collected from various websites. We have tried to use the most reliable sources possible, but again, the figures are completely unofficial.
Agent commissions are estimated at 5%
Obviously, some of the calculations on this site would result in infinity (ie, cost per home run when the player hit no home runs). These have been removed, mostly because they are not interesting. (Also, because infinity gives computers a hard time.)