Core game content without the DLC you are looking at about $60-65M
$38M for all the property (though you only need 1 from each category for the achievements)
$25M should cover all the vehicles, though you can spend more depending on what you choose to upgrade and how far. I think the Veyron SuperSport can have over $1M spent upgrading it.
Buying DLC packs simply adds the cars to the game - you still need in game money to buy them to race. Multiple versions of the Veyron were available, each with price tags of $1.6-3M