In article , Sacha
writes

We saw silk duvets being made in China. I think they cost about £300
over here and they weren't cheap there. Our feather duvet is one of
those with two layers but we've never found it necessary to use two.
Our house is pretty warm and rarely draughty, so one layer does us fine.

Not sure about ones with silk outers, but the cotton outer and raw silk
inner are considerably cheaper than that (otherwise I wouldn't have
one

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regards andyw