Sure, you could spend 3-4 hours driving from Brighton to central London and paying £65 to do it.
It doesn't come close with season tickets, hence the reason so many people chose to commute by train rather than driving. Also why people take the train rather than commuter bus services which tend to be cheaper
Also consider comfort - have you see how crowded those trains get, sometimes you might have to stand for hours on a long distance train. If you are able bodied man thats one thing, but if you are pregnant or injured, that's tought.
They are not suppose to be close.