Reproduction steps:
1. Open project attached (ReflectionProbePrefTest.zip).
2. Open Profiler
3. Start Scene
4. View DrawOpaque in profiler
5. Select All Reflection Probes
6. Turn them on and off, observing the change.

Expected result: The reflection probes should not (or by small amount) affect the amount of time it takes to do "DrawOpaque".
Actual result: DrawOpaque takes about 0.25 ms longer (depending on PC).

Reproduced on: 5.5.4p4, 5.6.3p2, 2017.1.0p5, 2017.3.0a6.

Notes: Reflection probes incur a draw cost based on the # of renders in a scene, regardless of whether probe or renderers are static, and regardless of whether the probe is touching anything.