What is more worrying is the thought that any jewelry you send may be worth more than the scrap value of the gold if it is sold at auction. What is the value of the stones that are taken out before the gold is refined?
This is a little unfair on the TV advertisers. They do indeed offer only a fraction of the scrap value of the gold you send them, but its typically around 30% not 6%. They are a business. They make no bones that they are not interested in the jewellery and will not be reselling it as jewellery, they intend to melt it down so are only interested in it as scrap gold.
The Which report is comparing the scrap price the TV advertisers offer to the retail value of the gold as second hand jewellery.
If you have gold to sell the best advice is to weigh it then go on-line, find the conversion rate from the number of karats your gold is to grams of gold and then look up the price of gold. This will give you a decent idea of the scrap value. You should be able to get close to 80% of this from on-line gold buyers or high street jewellers.