Same.
If its a game I'll be waiting for and buying upon release, and playing all the time, ill likely buy the DLC providing its got actual game content in it.
If its a game I won't play much, like Forza 5, then I simply won't buy it.
Likewise if the DLC is crap, and not worth it because it only offers cosmetic changes or other stuff im not interested in. I won't buy it.
Just vote with your feet as to what you feel is good and what isn't
rockstar have already released loads of DLC for free. There was:
The Beach Bum Pack
The Stimulus Package
Content Creator Update
Business Update
The Valentine Massacre Special
The High Life Update
I'm Not a Hipster Update
Independance Day Special
Flight School Update
all for free. Rockstar have said that the reason these are free is because of the income they receive from selling GTA dollars. There will no doubt be a story expansion like the ballard of Gay Tony, but these are usually good value for money and effectively add a whole new game for half the price.