Performance hit when there are many gizmos on scene

1. Open attached project
2. Launch scene "slow"
3. In Hierarchy, click on GameObject
4. In Inspector, adjust the Count to 200
5. Hold Right-Click and drag around in Scene view

Expected: There is no noticable slowdown.
Observed: There is noticable slowdown.

Occurring on: 2018.1.0a5
Not occurring: 2018.1.0a4-a1, 2017.3.0b10, 2017.2.0f3

.gifs attached in comments.
Note: You can start to feel the slowdown when there are 50 gizmos on scene, but the gifs don't capture that well. 200 gizmos was used to better illustrate the point.