JSPerf is a measurement tool, not a simulator 
For statistical reasons, you’ll get a more accurate measurement on 5m samples than on 40-50.
The message isn’t “you can only run 2.500.000 getters vs 5.000.000 direct accessors within a single frame” - rather “on average, getter / setter is 25-50% slower than direct access” 
I’m not saying setters / getters bad - I’d just measure the influence on the FPS on projects like FreeCIV, gpu-pathtracer, and on VR projects - these things will likely be more prone to losing FPS than a regular portfolio website with a single Blendor model.