If I've got my math right, caps being 250 gold...
A goldmine flag gives 4g per player, per second (I think.)
A cap lasts for 40 seconds. 4x4=160.
A cap on a gold mine works both ways. You get the money, and your enemy doesn't.
Thus, in a 1v1, 4x4x2=320, making it actually economically feasable to lock the flag every time it cools down.
Obviously, you wouldn't literally lock the gold mine that often. However, I maintain that keeping the mine or experience in 'semilockdown' by keeping an eye on it and a TP and Lock ready is quite possibly one of the easiest ways to win the game.