Immy,
You are correct, they do double dip if they buy them from you and sell them to me. What I have heard is that when a coin dealer buys a bag of $1000 face from you, unless he has a customer that wants to buy it, or a good walk-in market for silver, they will immediately call someone like Dillon Gage and lock in a price to re-sell the bag to them.
At that time it is considered a "Deal" between the dealers and the guy ships the bag of $1000 face to Dillon Gage and he gets the agreed upon price regardless of whether or not spot goes up or down. I have not dealt with Dillon Gage, but I imagine they do not pay full spot to the dealers either.
On the other hand they always charge a premium, "The Spread", if they sell coins to the general public, even after having made some money when they bought the coins to begin with.
Im not saying a agree with this, but only that they need to make some money to stay in business.
Here is an example from one coin dealers 24 hour hotline that I feel is too large of a Spread. I called it just now to see what he was offereing.
Hot line as of opening this morning, silver was at $15.76:
40% Buy $3.80 (per dollar) Sell $4.50
90% Buy $10.50 (per dollar) Sell $11.70
At $15.76 actual melt is:
40% $4.49 (per dollar)
90% $11.22 (per dollar)
So he is paying you about 85% of melt which to me is not a good deal to sell at.
Bottom line is you have to shop around and sell them at a price you are comfortable with, so you will not go around beating yourself up over it in the days to come.
CLZinTX