Why DLCs before game is even released fully?

Just to throw my two cents into the thread I’d like to say that I realize that electric, wankles, and diesels(admittedly diesels would be really nice to have) aren’t really worth the effort of having in the base game I would prefer a sequel with some extra tweaks to DLCs. with DLCs I rarely get motivated enough to get back into the game because normally they only add minor things and very rarely things that completely change the game, when they do completely change the game they could end up making it harder to play the original versions of the game, but with a sequel it would be fine to make significant changes to the core gameplay. just out of curiosity what are the expected prices for each DLC?