The list is fairly short (70 activities total). Once filtered it would be easier to simply display all matching activities.
Many of the "Low" cost activities have significant upfront costs. I wouldn't describe Archery as "low cost", nor describe Astronomy or a board game night as Free activities!
It was easier just to read the raw JSON than browse the site. ( The activities are https://www.whataaabout.com/activities.json and seem to be static, not based on parameters. )