I think it is less than 10 x as the diameter of the wheel has a huge impact on the ratio, but it has made a difference.
I have noticed several differences in free-er revving, a harmonic vibration at around 2800 rpm and smoothness is lacking at the upper end. Not all good but the smoothness just means some more to be done on the map to smooth it off whereas the std pulley would have smoothed this over with its extra mass. The engine does brake easier too.