Hello Russ. I could very easily write a few pages in response to your question. But I like the way Ken sums it up.
But I will add that when the big recession hit, it hit the price of cast iron as well. It was a buyers market for sure. But on the truly rare pieces they were and are bringing good money. And I think the trend is that overall prices have climbed in comparison to what they were during the recession.
And one more thing and then I'll shut up. Even todays prices are not near what they were, say twenty five years ago, pre ebay, pre internet, pre FB. During that time prices were very high. Some folks who still have stuff that they bought back then are trying to get those prices for their items. Its not happening because people put that stuff on the market whereas before you did not see that stuff. Some pieces I have never seen out in the real world, but they are on ebay.