While this is all very interesting, it isn't entirely accurate. The Koch bros don't even spend that much of their own money on politics, they get their employees to do it.
My wife worked for Koch, and was given childish 'seminars' that would single out and deride anyone who didn't want to 'voluntarily contribute' to the Koch's various organizations. They used Soviet-style intimidation tactics, and the most 'company-loyal' staff members were those who contributed the most money, usually $5k.
The whole thing is a giant back-slapping contest, just look at this article.