No, if we are holding stock was spot goes from £1350 to £1150, we make a "paper" loss of £200 per ounce on our stocks, with the same in reverse when gold goes up.
There is no way we could make this up with higher premiums. If we increased premiums from say 3% to 23%, we would wait a long, long, time before we sold anything. Our premiums are relatively unaffected by actual price levels, and much more by supply and demand. Even then, it would take a big change for us to shift our premiums by more than about 1%. As a dealer who "makes a market", we need volume trade, preferably in both directions, to operate profitably. There are times when all goes quiet, and we just ride these out. Having a numismatic side, and a wide range of stock and "products" helps out.
If we can keep purchases and sales in approximate balance, then we make our money by trading the premium, rather like a casino or bookmaker.
If we sell an ounce that we bought when spot was £1350, for £1150 plus 2%, then buy another ounce at £1150, we are happy.
As gold has increased in price more than it has decreased in the last 50+ years, then our stock-holding account will be in profit on a long term basis. I don't go out and celebrate when gold goes up £100, and neither do I think about jumping off Blackpool Tower when it goes down £100.