I have a ring valued and certified for insurance reasons at over ?1000, I can't get any jeweller interested in buying it. Cash converters would give me a nominal amount.
Valuation = what it'd cost you to buy another one at retail.
Value to a jeweller or pawnbroker = a small fraction of that. (And they probably charged for the certified valuation.)
It's much easier to say that you don't buy second-hand rings etc than to say 'actually, the markup on the stuff we sell is
huuuge and hence the real value of the thing you paid us /someone lots for is low'.
A client has offered me a necklace for an overnight, it is very beautiful however I've no way of knowing whether he bought it for ?1000 or ?10.
If you'd buy the necklace if you had ?1,000 or ?100 or ?10 cash in your hand, that what it's worth that to you.