Economists can actually measure the value of insider connections:
[L]obbyists connected to US Senators suffer an average 24% drop in generated revenue when their previous employer leaves the Senate. The decrease in revenue is out of line with pre-existing trends, it is discontinuous around the period in which the connected Senator exits Congress and it persists in the long-term. ... Measured in terms of median revenues per ex-staffer turned lobbyist, this estimate indicates that the exit of a Senator leads to approximately a $177,000 per year fall in revenues for each affiliated lobbyist.
The fall is steeper, the researchers find, when the departing member of Congress sat on a powerful committee such as Appropriations, Senate Finance, or (on the House side) Ways and Means. Lobbyists who are ex-staffers are also more likely to quit the lobbying business once "their" member departs office. Incidentally, actual per-lobbyist revenue is lower than you might assume from the above figures, because many lobbying contracts are shared out among several participants with each individual getting only a portion of the proceeds. (Jordi Blanes i Vidal, Mirko Draca, and Christian Fons-Rosen, "Revolving Door Lobbyists," via Alex Tabarrok).
If you needed another reason to vote against that unsatisfactory incumbent this fall, reflect that by doing so you'll also be dimming the stars of his or her unsatisfactory ex-staffers.