I'm not into custom seats at all, but considering the price of a bare bench seat frame being in the $600-700 range I would think that a pair of formed metal wings like that could be a $150 to $200 option, but that's a plain old WAG, not a SWAG My logic is maybe you could add ~ 25% of the bare frame price for the wings. Others may disagree with that approach, but I think that's the discussion you're wanting here?