have you seen those "invisible" watches that the gears and everything are made of sapphire so they're entirely clear? quite expensive though. over 15k i believe
In the perfect light, they might be able to make it look that transparent. But there is always a reflection. I've got polished sapphire, highest optical quality you can get, sitting on my desk right now, and it's REALLY transparent, but there's still always a reflection. They probably put some anti-reflective coatings on it to minimize it, if it's really fancy they could probably get it down to really low reflections but it's always wavelength-dependent. They could probably use a light for the photo that best-matches their anti-reflective coatings and get it down for the picture. Or digitally enhance it later.