I tend to value mark's info more than many others. Ask him how much $ he has in turbo inventory at the shop! He's also a tuner, with a dyno, and unlimited access to customers trucks who wanna spend the money.
So why were they even compared in the first place. This is very simple people. A gtx 4508 has a 80/108 compressor and a 87/80 turbine with 1.01, 1.15, 1.28 and 1.44 t4 housings availible. The s480 is very close in size on the compressor side. Now the turbine side is another story. There are 4 turbine wheels availible. 83, 87, 92, 96mm. T4 housings are .9, 1.0, 1.10, 1.25. T6 are 1.1, 1.32 and 1.58. From the info i just listed it appears that an apples to apples comparison can in fact take place. So unless all of these chargers had the same size turbine wheel and relatively close sized turbine housings this comparison is a joke.