Yes perhaps I was unclear, when I talk percentages I'm talking premium over/under spot oz-for-oz, but of course more gold = more money total. I certainly would expect to be putting more money into the equation, and I'd be expecting to pay a lot more than £800 to be honest!
It seems the way dealers operate (understandably) is they'll buy your gold usually at a % under spot (I was offered 5% under spot) and they'll sell you gold at a premium (in this instance 5% over spot), which equates to a 10% cost to trade in oz-for-oz or a double bite-of-the-pie for the dealer effectively. Effectively it's no different than if two separate people made two separate transactions (one to sell and one to buy). My hope was there may be a dealer that would take a view on the transaction as a whole so-to-speak, but it doesn't sound like there is. Quite understandable given it must be a relatively rare scenario.
To give a random example... if you have a games console to offload you can head to your local CEX and sell it or trade-it-in against something they have in stock. If you trade-it-in your item is worth more than if you just outright sell it. The shop effectively is willing to make less margin on the incoming new stock (less-not-none), in order to secure the margin on the outgoing stock.
I've definitely overcomplicated this haven't I? Or have I spotted a gap in the market? Melon's Precious Metal Trading Exchange, coming to a high street near you 😄