Parking near Nats stadium is like $20 at best.
Metro is probably cheaper, but such a mess I hate to take it. Last time I tried, one of the other trains derailed and held everything up. Only been to one Nats game this year, supposed to go to one more at the end of next month to see Miami via free tix from work. Was supposed to go to the Pittsburgh games a week and a half ago but gave the seats up because I rescheduled my vacation for that week.