I'd assumed it was for fiction - good point King N.
Continuing to assume it is for a work of fiction, what the OP might want to do is to trawl through auction house catalogues and find something of the right period and price and describe that in the book, rather than first inventing the look of the jewellery and trying to find out its price. Unless of course the appearance is already key to the story.
Just a thought on speeding up the research. I'm keen on good research, but it can be time consuming, so ways of minimising research can be useful.