We opted for the unguided walk, and were utterly underwhelmed. It felt like walking through woods that could have been anywhere, we saw and heard absolutely zero wildlife, and the view from the hanging bridges was not particularly spectacular. For that, we paid $88 for a family of four. We were very aware having done the guided walk at Arenal that it's hard to spot wildlife even for the guides, but it seemed like in general there was much less to see. No way should they be charging $25/adult for a self guided walk.