FItemRepairCostMult

Default 2.0, means 1% condition repair costs 2caps. (According to kschenk in primary needs)

I'm sure there's a multiplier for item value in that formula: Maybe...

RepairCost = ItemValue * %toRepair * fItemRepairCostMult 

but I'm completely confused as to why repairing at item might cost more than a 'new' full condition item...

This is because 2.0 means the price to repair is 2.0 x the value increase in the item. For example, if I have an item at 0 condition so 0 value which is worth 1000 at full repair, repairing it costs 2000 caps (or 1999 or something). I'd say...

RepairCost = ValueIncrease * fItemRepairCostMult