Just to drop a number: With current C31 code Vega 64 does 1.1 g/s at 180 W (settings: 1380 / 1000 @ 0.912V) making it the 2nd most profitable algorithm after CNR for V64 (!!!).
You are totally wrong with your calculation. Vega64 can easily make 50+mhs eth with lower than 180w power consumption. ))
You didn't get what he meant. 1.1g/s @ 180W vs 50MH/s @ 160-170W is the comparison which should be used. I am pretty sure you're going to argue that 160-170W, this is Vega64 actual consumption measured at the wall. Vega56 is slightly (150-155W) better for ethash.