Spend a week camping at a state park nearby with the family. About $40 in transportation costs round trip for the whole family. Maybe $200 in food/snacks/other consumables. $70 for the yearly parks pass+ $15/night for campsite = $175. If I don't already have camping supplies, I can get decently kitted out for the family for this kind of camping for like $400. It'll last me a bunch of trips but let's assume you've got nothing. So that's like $815 for the first time, $415 every other time.