I got mine years ago when they were cheaper, but IIRC, they are a bit over $100.
I still have my Netties Bags, but never use them any more. True, they are a lot less expensive. But they are very narrow, and your foot slipping through them in the tumult of a rapid could be a problem. Plus, until you have time to re-stow them in their sack, they continue present an entrapment hazard.
The Rescue Rung isn't for everyone, but it's a great product.