I regularly practice each of them and barely spend any money

hiking: I just do light hiking, and all I need is a couple of sandwiches, a backpack and my boots. And plenty of water. Plenty of hills/mountains around helps, that's true

biking/rollerscating: you can get a decent used bike for about $100

picnic: just the food, and you need to eat anyway

board games: unless you need to switch the game every week I'd say you're covered with about $50 per year. We mainly play Settlers of Catan and Chess

lan party: I guess it depends on the games, we don't do this much anymore, but we're pretty old school when we do (CS, Starcraft 1, Worms World Party)

There's probably lots of other activities like that, for example we play soccer/foot tennis on a public field, and all it costs us is the price of the ball