In fairness, many of those people could make more money in the private sector.
I see a lot of $42,000 salaries on that list. That doesn't go very far in the Washington, DC market.
In fact, that area sucks.
It's an area where they really expect YOU to pay for the privileged of working there. A common question during the job search in DC, "How do you live on that here?" The answer, "well, you live with a lot of room mates..."
So you have a huge community of over-educated, rich kids who can "afford" (read idealistic or supported by their parents) there, managed by wealthy people who have learned to manipulate the system to earn a fortune.
So while those White House employees make reasonable salaries now, they'll parlay and network that into high paying positions with law firms and lobbyists next year..