Cables handle 60W not by being thicker, but by allowing a higher voltage. The thickness of the cable is decided by amperage, not voltage. So when operating at

Cables handle 60W not by being thicker, but by allowing a higher voltage. The thickness of the cable is decided by amperage, not voltage. So when operating at 90W the cable only needs to be a tiny bit thicker and negligibly more expensive than a normal 15W cable.