How come wordpress demos get good pagespeed results?

I usually test themes on google pagespeed before using. Invariably, they fetch a score above 60 despite using tons of pics/animations/sliders and dozens of javascripts & CSS & google-fonts.

However, with only a layerslider + couple of optimized pics (test site) seldom fetches more than 38-42. I can understand good server response as one reason, lazyloading as another. Yet the difference of 20 points is a bit too much. Any ideas what could be the plausible reason?