Yes, I think so. Otherwise you are suggesting that the ebay prices are falsified, rigged and untrue. I belive that a very small minority of them really are untrue (A classical example is letting a friend bid on the auction.), but the large majority of them are true.
The market of old Mopar parts is like any market working under the rules of supply and demand. High supply - Low demand gives low prices and Low supply - High demand gives high prices. As we all know by now: Mopars are hot
Nowadays you can even fry eggs on a-bodies. With many wealthy men who wants to buy the dream car of their youth (very generalized), it all can become like this.
Any positive to say? The rapidly increasing repro market gives all of us with not-so-thick-wallets a chance to build something good looking. (The drawback with these repro parts is that they are not always easy to separate from the real deal, making life hard at the swap-meets. Non of us wants to get fooled. We all want to know what we are buying.)
I also belive that the new Challenger will cool down the market a bit. I think it will be a very competitive car and I think that there are quite a few of us who prefer the advantages with a new car (without sacrificing styling, performance and such).
Is it a good investment to buy expensive parts today? Nobody knows. Only the future will tell.