$15 works well for me when solo, probably a push when bringing 1 person, and not so good when I have 3 or more. I like the social aspect of it, having a chance to talk Nats to and from the game.
Maybe they could also play the post-game show on the radio on the buses.
I get what people are saying about Balston, but I suspect the cost of a bus isn't that different from Reston vs Balston given the block of time it is unavailable for alternate use.