Firstly, the financial value of your collection is the amount someone else is willing to pay for it.
Trying to put a fixed value on your own collection based on factors other than what someone else is willing to pay for it (i.e. the market value) seems a bit pointless to me. You can say, "I think my collection is worth $X," but if no one wants to buy it for that much, then it's not worth that. I'm sure we'd like to think that we have financially valuable collections but the truth is that the value of all of our collections is far less than we actually paid for them.
To take this further, you'd have to determine the resale value of second-hand items based on condition. Unless your collection is still in shrink wrap, we are talking about non-new items which are sold far less frequently and for less. Game components are not like old coins or old baseball cards or some other types of collectables where condition is important but 'newness' doesn't really exist.
Take the Cathars as an example using sale history on the BGG marketplace. There have been 142 sales and 131 of these (92%) were in new condition. Similarly, the Tunnels is 80/85 sales (94%) in new condition. The different currencies and the small sample size of the various non-new conditions mean that price comparison cannot be done accurately, but the takeaway for me is that people aren't that interested in buying non-new versions of even these rare expansions. Or perhaps precisely because they're rare, people fear fraud and only want new versions for which authenticity can be confirmed. Basically, there is not much market demand for your Carcassonne collection.
At the end of the day, our collections are extremely valuable to us personally mostly for sentimental reasons. This does not translate into re-sale value, which is the financial value. The actual dollar amount doesn't really mean anything to me since I won't sell my collection. But if I had to take a wild guess, I would be surprised if anyone would pay much more than €100 for my essentially complete Carcassonne 1 collection.