GUIUtility.BeginGUI taking up 20% of frame with no GUI

I've just got started profiling our game, and I'm finding that GUI.BeginGUI is taking up around 20% of frame time when deep profiling (sometime as much as 65%). I thought perhaps we were doing something stupid in our OnGUI call(s) like repeatedly setting the skin or something, but it turns out that if I define out the body of our OnGUI function (i.e. there's no GUI rendering at all) we still lose that 20% of our update time to BeginGUI.

Looking deeper into the call trace, pretty much all of that time is taken up by calls to String.ToLower and *Hashtable.get_Item*, but all these calls fall below EditorGuiUtility.LookLikeInspector:

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So my question is, will this EditorGUIUtility time still be taken up in a standalone build, or can we depend on getting that 20% or so of frame time back in those builds? And if this behavior will still be around, is there anything we can do to kill these apparently needless calls?

You'll get that 20% back - it's the rendering time for the editor and the profiler, Editor* classes aren't even included in the build