"Significant savings. Scaling a 960 pixel image that is 79KB is size to 240 pixels wide yields a 86% size reduction, to 480 pixels is a 58% size reduction, to 720 pixels is at 23% size reduction."

I think the reduction is more if we consider that a 240 px image is 1/16 of a 960 px image or 480 px image is 1/4 of 960 px image.