It should cost “enough”. What do I mean by that? It depends. Literally. Also the (money-) cost of after purchasing a game is important too, with DLCs and micro transactions as well. And if you just “rent” a game as service (multi player only in example) or if its a single player game that you can keep and is not dependent on servers. Besides downloading the game off course.

That’s why I don’t like generalizations at all. This is a bit more complex to answer than it seems. I genuinely think there are games or may come out in the future, which might be worse the 80 Dollars or Euros. Others not so much. A game should cost as much as it is worth it. And that upper limit is only defined by the game itself (and whats available otherwise too off course, that is not simple).