I built a benchmark to stress GetComponent in Unity, in response to widespread concern over its performance.
After building the test, I've decided to share it, since I could find no real online sources besides some old and controversial and user benchmarks. This was designed to address a major complaint with those, namely that simply running GetComponent repeatedly in a loop does not produce valid results, due to compiler optimization. In mine, a different component is chosen at random each iteration.
Your results will depend on your device. On mine, I can run 1000-2000 iterations without any apparent stutter in the on-screen movement.
I hope it is helpful for someone.