I believe Ironworks should give you +$1 for the Silver, and here is my reasoning:
I'm going to dinner with my wife. The sommelier/waiter comes and explains to me that if I choose the beef entree, I get a red wine; if I choose the fish entree, I get a white wine; if I choose the vegetarian entree, I get a rosé wine. I decide I want the filet mignon, and tell the waiter accordingly. But my wife interrupts: "No, honey, you need to be on a diet. He'll be having the halibut instead." Surely the restaurant will now bring me a white wine.
Trader says, "you were going to get something, but instead you're getting this." To Ironworks, all it should see is that you are getting a Silver. It doesn't know if you chose the Silver, or if you chose the Great Hall but something else happened to get you a Silver. It says, gain a card of your choice, I chose, and I ended up getting a Silver. The fact that I chose at first to get a Great Hall, and then chose to do something else to end up with a Silver instead shouldn't affect Ironworks any more than if I took a Great Hall, but then changed my mind and took a Silver instead.
I like this outcome because:
A) It is weird to say that I get nothing for revealing the Trader, when I could have just gained the Silver with Ironworks directly;
B) This interpretation produces the expected result with Possession, namely, that Possessed players should have Ironworks bonuses.