Of course you are going to be behind both the premium and the dealer markup when trading with a dealer. That is why you need to work the far ends of the swing. If a magic bullion swap shop existed, you could trade bullion every single day in whatever direction the ratio moved. Because it doesn't, you have to work the extraordinary highs and lows of the ratio trend. Those extraordinary highs and lows do exist and they are not fleeting. They last for months at a time.
When the ratio is favorable (either high 70s or low 50s), go to a large show with lots of dealers. Ask a number of dealers for their best even trade deal and take the best of the bunch. There is no "jump in price" consideration whatsoever. It doesn't matter whether you bought your bullion, dug your junk, or traded for it. You don't care (and the dealer doesn't care) what the spot price is - only the trade-trade matters.
I have done this trade in both directions and it works as advertised.