In response to your updated OP: no they shouldn't. That would lengthen development time. DLC is supposed to (well in my opinion at least) keep folks interested in the game over the months after release. I'd argue that you can sell more games over the coming months, and keep people invested in your game, by releasing spaced good DLC expansions/game modes etc.
When devs release DLC day 1 and charge extra; well I think they're being real twats tbh. I see what you are trying to say but technically, by my definition, it wouldn't be "DLC" if it was ready at release. It would be part of the game. In which case, the rising price of games would cover it.
So I respectfully disagree.








