Why is my thin glass dome taking so much light away from what is inside? I made a rather simple roughed-up gold material which you can see here. It has nice highlights and looks OK on the teapot, it works a lot better with the actual mesh I'm using, which is a scan of a clay sculpture. Overall it gives a nice gold-leaf effect.



Then I made a thin glass display dome taking half of a sphere, extruding the equator down, and applying subdivision and solidify (0.001 thin, IIRC). I used a simple, all-white, all transparent Principled BSDF glass material with enough of a roughened up clearcoat to simulate it being a little greased up. You can find the blend file here.



However, you'll notice that the material under the dome is considerably darker now. It seems like less light is getting through the glass material. I mean, that's OK, I was expecting some light to get lost in the process, but this looks a bit much compared to some of the references I've been staring at for hours: the following, for example, is surprisingly similar to what I'm trying to achieve.



I tried fidgeting with the light settings, and the glass settings, and the light paths, I even tried to increase the max bounces, and change pretty much any number that seemed correlated to light but I couldn't get any closer to the effect I want. Increasing the intensity of the light is not a solution because it affects the rest of the scene. I thought of adding fake lights on the inside of the dome but that opened a whole different set of can of worms so I quickly retreated.

I can't shake the feeling that I'm missing something obvious. I've seen very similar scenes done so I'm confident this can be done. See this post for example, though I couldn't figure out exactly how to apply their advice to my scene.

Hints? Pointers to RTFM?
Notice in your reference image that there are multiple light sources clearly visible through the reflection on the gold egg. With any type of reflective/metallic object, having objects/lamps to reflect is important when trying to make the object not look flat.

I made a few changes to your scene to fix up the lighting:


I enabled smooth shading and auto-smooth normals on the glass dome, which also allowed me to reduce the number of subdivision surface iterations down to 2. That helped reduce render times a bit.
You should also consider moving the subsurf modifier on the glass dome before the
solidify modifier. When you apply the subsurf after the solidify
modifier, you end up flattening the solidify modifier by quite a bit.
I increased the size of the lamp from 0.1m to 0.44m. Glass refracts/and reflects light, so some of the light rays that would have struck the teapot without the glass would be refracted away from those points on the teapot as demonstrated by the shadow on the ground. That contributes to the perception of the gold being flat/dark. It also lets the light comes in from more angles, so more rays can strike the glass at points that make
them refract onto the teapot.