Sounds about right, it's not magic. AFAIK the Metal support in Blender is not very optimized yet (it's brand new) but even optimized I don't expect it to come close to an RTX 3090. I still find the results amazing, for the amount of power this thing needs if it reaches 2x slower after optimizations, that's massive. Don't forget that the Ultra also includes the CPU and RAM in the power consumption.