Yes, gold plating or a solid gold body makes so much sense in a meter designed to test mains voltages...
In order to be sellable on the open market, it would have to be put through the whole testing process separately from the standard meter, and would fail on items like double insulation. Creepage and clearance issues would be a swine. It could only ever be sold as an ornament, not something that is intended to be used around electricity.
Cat III 300V is tested to 4kV IV is 6kV. I wouldn't want to be holding that meter...