i would gladly pay 30€ / 30$ for a game and the prospect of DLC for about 15€ / 15$ and 5-10€ / 5-10$ left for micro transactions. while the DLC would remain optional, the micro transactions would provide a small / medium boost in the game but wouldn't compromise the storyline with, let's say, an uber weapon which normally appears in late game. the DLC would add additional content over the course of one year.
that way i could buy the initial game with 100% content for 30, tie loose ends up over the course of the year if i WANT to invest additional 15 and still have financial room for small boosts.
that would be a fair way to treat a customer and would give him a lot of freedom back. but that would ruin their profits.