First question that comes to mind is how price is formed. As person above said, upgrade items have a discount, if you have its component. Your items is T4 tier and created from two T3 tier items. Therefore, logically, it should be free. The idea itself is clear, combine two items into one, saving slot. But still, it lacks some additional buffs from its components. Maybe, additional resists are gain, if you have 50% health or less.