Essentially, I have a bit of a problem with getting four of any resource being called a "monopoly" bonus, because monopoly implies that only one person can have it. However, there are often 8 or more resources of each type in the galaxy, and therefore, you can easily have 2, 3, or even more races with a "monopoly" bonus for a given resource. I think a better term would be to call it an "Abundance" bonus, representing that you have hit some threshold of supply to give you a bonus. And heck, maybe you could even throw a true "monopoly" bonus for having the majority of the resource in the galaxy that would give you another level of bonuses. But I think as it is now, it's a bit confusing since it implies one thing but represents something else entirely.