In Fortnite (PC, PS4, Xbox One), there is an answer to the question of why it is already available for €40 in stores when the game is still in Early Access. We Europeans are to blame.
We have reported more than once on the somewhat confusing sales model of Fortnite:
Fortnite: Free-to-play or Buy-to-play? What is the deal with Early Access?
Fortnite is technically Free-to-Play, but it is still in a sort of “Closed Beta,” for which access can be purchased through Early Access.
The confusing part: The Early Access version is sold as “Retail,” i.e., in stores. This makes it look like a regular game on the shelf or like this: a boxed game from the online retailer Amazon.

Now there is a statement regarding this. The Creative Director Darren Sugg explains why they are doing this.
European market still prefers boxed versions
He says: They received numbers from Sony that two-thirds of all Europeans still only buy games “physically,” i.e., in stores in a package. They do not buy digital games through the PlayStation or Xbox Store or through Steam.
Suggs states: “If we want these people to be able to participate in our Early Access and if we want to be fair to everyone, then we had to bring Fortnite to stores. Only in this way can we allow these people to participate in our testing.”
Here there are differences between North America and European countries and Russia. Since they want to be fair to everyone and treat everyone like a “first-class citizen,” they decided on this distribution model and brought Early Access to stores. Many observers find this strange, but “Other countries, other customs.”
Nevertheless, most Fortnite players now play digitally. Suggs revealed this in an interview with the US site GameInformer.

Fortnite has about 60 hours of quests in Early Access
The current version of Fortnite includes about 60 hours of narrative quests and most core features. However, it is evident that some tutorials are still missing. Player feedback here is: “That’s not so important, we figured that out ourselves, just bring in more features.”
Currently common even for retail games is a “cash shop” where you can spend real money, how to avoid that, you can read here:
Fortnite: Guide – How to farm V-Bucks – Never spend real money again!