High cost of CullAllVisibleReflectionProbes

I've noticed a very high cost of SceneCulling in general, and CullAllVisibleReflectionProbes specifically; even though there's only one reflection probe in the whole scene, the cost of CullAllVisibleReflectionProbes is still 0.75ms in the Editor, and 1.75ms on PS4.

I've been told this cost scales with the number of renderers - is that right? Can you give me more specific information on this; we're using deferred rendering, so does the cost only scale with the number of draw calls in the forward-lit transparent pass?

Is there anything more I can do to reduce this cost, and SceneCulling in general (which gets up to 6ms on PS4)?