Actually, I'm past the point of using sarcasm. You might be right that baseball needs a salary cap, but your two main points are absolutely incorrect.
There are plenty of players, over the past decade, that the Yankees have had varying degrees of interest in but didn't end up signing. This happened for one of two reasons (or a combination of both). Either that player's salary demands exceeded how much money the Yankees' could spend, or the Yankees felt that the player's salary demands were above how much he was worth.
Additionally, while the Yankees have given out some huge contracts, they typically aren't credited with giving out the landmark contract to a position player, or the landmark contract to a pitcher (over the past decade).
EDIT: The Yankees enjoy an advantage that no one else does, and it helps them win. There is no question about it, and it's something I readily acknowledge. However, lets not overstate this advantage to an infinite degree. It simply isn't factual.