I think you have misunderstood their system a bit.
You have ALWAYS had to pay money for MS Points, which is the currency used to pay for things from the Xbox Live Marketplace. You pay money, you get points, you use those points for additional game components (such as unlocking the versus mode in Resident Evil 5) or to buy completely new games.
These Microsoft points are NOT Gamer Points. Gamer points are earned by getting achievements inside a game, and cannot be redeemed for anything. They are only there to show how much of a gamer you are (logically, someone with a lot of points has either played a lot of games or has maxed out a few games completely).
This goes back to the debate about DLC in general. I am of the opinion that while it sucks to pay money for features that should have been included in the game (such as buying an unlock code only), I do understand that more and new features and campaigns require time and effort to develop them, and the people who do this should be compensated.
The Fallout 3 DLC are totally new additions to the game. I think it’s fair to pay if you want to play those. I do not agree with your thought that they should be free, why should they, they weren’t included with the game at all and they took time and effort to create. New Rock Band songs are new content and I don’t mind paying for them. The Resident Evil 5 versus mode update I will not buy, not only do I oppose the idea of unlock codes (which it pretty much is), but I simply refuse to pay to play games online when I have tons of PC games that do so for free.