It's an interesting question, and I'm really just an arm-chair SEO when it comes to the world of extreme money keywords. What I do know from experience is that there are a lot of these extremely profitable keywords. With a little research you can figure out what the top 10-100 keywords are, by traffic, in the world or just in the USA.
Some are totally 100% owned by big corporations who get the majority of the hits for that term and expanded phrases. Some might say that's legitimate because that big corp is the best result for that word. But there are plenty of other keywords that are owned by (formerly) regular webmasters who are now on top and fighting to keep it that way, with a sizable incentive to do so. These keywords are highly competitive and those webmasters will do anything it takes to keep the payday rolling in.
Some are totally 100% owned by big corporations who get the majority of the hits for that term and expanded phrases. Some might say that's legitimate because that big corp is the best result for that word. But there are plenty of other keywords that are owned by (formerly) regular webmasters who are now on top and fighting to keep it that way, with a sizable incentive to do so. These keywords are highly competitive and those webmasters will do anything it takes to keep the payday rolling in.