(I'm talking about spies that spy on their own country)
Without your country, there wouldn't be you. How do these people live with themselves? And plus the ones who are spies or who are in on the top secrets are usually pretty well-off and accomplished (you'd have to be entrusted with top secret government stuff). Why would they want even more money than they already have?
If offered the chance, say, for a payment of two million dollars, would you be a spy?
An undercover spy.