A real fast rope costs about $1000. A gym climbing rope costs about $100 (depending on length). 30 m of 11 mm climbing rope is a little over $100. I was lucky enough to get given two retired 11 mm ropes from a climbing buddy - these ropes were past it, having arrested too many falls for safety - but braid eight of them together, and even this old rope is strong enough. In addition to plenty of 10-11 mm diameter rope, you'll need a carabiner, a method of securing the carabiner to a wall, some insulation tape, an assistant or two, patience, an Exacto knife and a BBQ lighter.