Reproduction steps:
1. Open new Unity Project
2. Enter Play Mode
3. In Game View, rapidly move mouse around, with its polling set to 1000
4. In Profiler window, Editor mode, observe performance

Expected result: Performance does not slow down
Actual result: Editor performance slows down significantly

Reproducible with: Razer Viper Ultimate
Not reproducible with: Steel Series Rival 600, Steel Series Rival 110, Logitech G903, Razer Naga Chroma

Affected Unity versions: 2018.4.35f1, 2019.4.28f1, 2020.3.11f1, 2021.1.11f1

Notes:
1. The issue is much lesser when outside of Play Mode or when moving the mouse around in a Build
2. The slowdown seems to be correlated to the polling rate of the mouse. Setting it to 100 nearly negates the issue.