I was quoted about 1500 to retrofit a system to existing iron gates.
I did alot of research as I intended to fit myself, but I got scared off by all the reports of them not working...... even after a professional fit.
The next week I met somebody who had a set..... guess what, he couldn't get them working.
I think if you are prepared to spend 1500-3000 on a proper system, and are prepared to pay to have it serviced, fixed every few years then they are great!