I feel that age does allow for a markup above the cost of replacement with new cigars but sometimes I think people get carried away.
For example, I have been trying to get my hands on some CC from 1987(the year I was born) for awhile now. I have posted some WTB adds multiple times on other forums that allow for the trading of CC and so far I have only received one response. The guy had a friend who had a box of 1987 Ramon Allones Gigantes EMS that he would be willing to part. Only problem is he wanted $2,000 for the box.
Now, I was looking for more of a box of smaller/cheaper cigars or just buying a fiver because I knew I probably wouldn't be able to afford a whole box of cigars of that age on my college students budget. However, it seemed to me that the price he was asking was too high either way. I'm not at all knowledgeable in the field of aged cubans but from the auction catalogues I've seen for overseas cigar auctions, $2,000 could get me some very rare and sought after cigars.
Maybe these Ramon Allones Gigantes from that era are some sort of great vintage cigars but the price seemed very high. So the search continues for me.