I just checked my DMG 3.5 and it says it costs an additional 2,000gp for any magical enhancements for Cold Iron; so it would be a minimum of of 10,000gp to make it Holy, 8,000gp for the +2 Weapon Damage/Hit Bonus, 300gp for Masterwork, and Double Base Cost 30 for the Cold Iron Longsword.
10,000...