Thanks for the tip! I would agree that you don't need to book in advance except many times you don't want to spend your time bookings activities when you could be doing them. I like to book most activities in advance and then leave some days open for whatever happens.
The price varies in Monteverde depending on the company you go with. There's a couple lines that are short and not that sweet. Look for the long high ones!
See a virtual tour of the
Costa Rica Zip Lines we went on here..