Unlike MLB, the only thing guaranteed is the bonus and the first year, and of course the bonus gets prorated against the cap for the duration of the contract. Paying out the huge bonuses can bite a team in the ass if the player has a career ending or debilitating injury or just fades in performance - that's the chance you take to beat the cap when signing somebody good.

Baseball, I remember somebody like Rickie Weeks and to a lesser extent Ryan Braun who were like millstones on the Brewers financial books for years when they faded due to injury or whatever. I assume there are a lot of other examples that could be cited on other teams.