Pricing in GOG can be a touchy topic as you may be feeling. :)
As you are from Poland, I can tease you directly and ask why you have this communistic approach to the price of games. Afterall, no one is forcing you to buy, you want to buy, if the price is right - if the price isn't right - well life goes on doesn't it? ;)
Anyway, if you are not satisfied with the direct answers you got, on the service aspects of what you are buying, on the rightsholders determining the price. Maybe you'd be interested in considering how nominal price values should be compared to other products - 10$ used to buy a lot of food - now somewhat less - so the value of the game has in fact reduced, even if the nominal price didn't change.