(Especially those with a penchant for D&D)
Dungeon Master's Guide II
"Vest of Legends"
+5 Diplomacy (continuous)
+5 Perform (continuous)
+5 effective levels for determining Bardic Music effects (use-activated)
Spells used: Eagle's Splendor (2nd level), Greater Heroism (6th level)
Cost: 16,000 GP
What I need to do is figure out how they reached this estimate.
Guidelines for pricing magic items are here:
According to this, the continuous-use skill bonuses are their enhancement squared, times 100 GP, or 2500 GP each. Let's assume that covers the Eagle's Splendor portion of the cost, since there is no actual enhancement to Charisma from this item. Since these are complimentary effects, they are either added to the cost at 75% and 50% each, or both at 50% cost.
The Greater Heroism is more confusing. As a 6th-level spell, an 11th-level Wizard is needed to cast it. This is a command-activated power, since it only works in conjunction with Bardic Music. It also does not actually cast Greater Heroism, but instead provides a portion of the related bonuses in conjunction with the Bardic Music effect (Inspire Courage/Inspire Greatness/Inspire Heroism/Fascinate/Suggestion). So some fraction of the cost must be applied. (For comparison, a ring that allowed the wearer to cast Greater Heroism as an 11th-level caster would cost 6 x 11 x 1800 GP, or 118,800 GP, likely then divided by uses per day)
The DMG II apparently just wanted to be confusing. A much better build would use the 4th-level spell "Protégé" from the Spell Compendium: for the purposes of Bardic Music only, the caster imbues a sentient creature with a Bard level 1/2 his own. Since Bards can cast 4th level spells as 10th-level casters, this would imbue a +5 effective Bardic Music level into the Vest's wearer. Now, I'm still wonky on how you would get the total price down to only 16,000 GP, but at least this method makes more overall sense than using a partial-cast of Greater Heroism.
So, mathematically, how the heck did the DMG II authors estimate the cost for this Vest??
Person who calculates it out using reasonable interpretation of the rules gets an Epic item named after them (or their character)!