1) It's hard to believe that if the DLC is a city it'll be larger than SA - SA is larger than the city in GTA4.
2) Microsoft paid $425 Million for WebTV. They paid $1.3 BILLION for Live Search. Look how great those turned out. $50 million is pocket change to them.
3) The DLC will be a few side missions. Kinda like the RC shop in SA. Everyone who bought the 360 for the DLC and ends up having to pay for XBL will be pissed.