What if someone who knew the secret wrote a book explaining the whole truth to the world, how they did it, why they're doing it, and what the actual shape of the earth is. Wouldn't they be able to benefit by making lots of money on the book, instead of hiding the secret and just being paid by the government? Don't you think that by now someone would've thought of this already?
It's possible, but there are quite a few factors to deal with.
First, they'd have to be in a position to know of everything.
Next, they'd have to work out that they would actually make more money with this book. Given that they get an annual paycheck of a large sum of money, I can't see a book like that working out to be more profitable (depending on their age). After that, they'd have to compile all the evidence (assuming there even is any) without letting others near the top find out.
Not to mention that even if the book did come out, they'd have essentially the entire world against them. Experts and such would be brought in and it would essentially be this forum (with Gulliver and sokarul-type people) multiplied by 100.