Think about what you wrote. Is this the type of person you want to be ?
There is no easy answer to your question. You can rationalize this as taking advantage of an opportunity or seeing yourself–in your words–as a “sell-out”.
As another poster asked, it would be interesting to know how this opportunity arose for you.
P.S. A similar dilemma is faced by lawyers who want to practice in the area of Environmental Law. In order to pay their bills, they are often faced with the option to work for corporations who pollute the environment even though they are environmentalists.