That listing is up there for quite a while. It's highly overpriced and I think I can back that up.
Let's break it down a bit. Remember that we are talking about sealed items. So, we shall take sold listings under consideration - if there are any - and also exaggerate about the price a bit, just for laughs.
HeroQuest Core Game: I've seen it around 300 Euros, regardless of the version. So lets say 400 EUR.
Kellar's Keep Expansion: Usual price is around 100 EUR. We'll say 150 EUR.
Return of the Witch Lord Expansion: Same as Kellar's Keep. We'll say 150 EUR again.
Wizards of Morcar Expansion: It's the UK version which is much sought after. Latest sealed item sold was 400 EUR. We'll say 500 EUR.
Barbarian Quest Pack Expansion: I've seen a couple of unpunched sold for 400 EUR. Considering the shrinkwrap and our little help, lets say 600 EUR.
Elf Quest Pack: Pretty much the same as BQP. Let's say 600 EUR.
Adventure Design Kit: I've seen them come and go at around 40-70 EUR. Sealed and bumped by us, lets say 150 EUR.
Please note that the listing is missing the AtOH expansion. Funny, because its not that hard to get, compared to others.
Also, note that when selling a "lot" which is what this really is, you want to lower the total price a bit in order to lure buyers. You don't blow the price up to scare them off!
So, adding up the above "through the roof" prices, gives us a total of 2550 EURO for the lot. He is asking for 100 EUR shipping which is decent considering the lot's price and the insurance. Final price for the buyer is 2650 EURO. Removing 13% ebay and paypal fees, the seller would eventually get 2650 - 344,5 EUR = 2305,5 EURO.
At the moment, he is asking for 4850 EUR, shipping included. Minus the 13% fees, he would earn 4219 EUR. So, he is asking almost double of what we thought as exaggerated prices would be. He knows he won't sell that. I think that this is a listing in order to welcome possible buyers into other listings of his.