Article says $10.50, I found some on ebay really quick for $8 with free shipping. Basically the issue is the keys can be easy to hide and have no metal for metal detectors. I have known for years that cuffs are easy to pic. So….you would think by now they would have developed and started replacing cuffs with a more secure version. Of course the other method would be to use zip ties.
http://www.nydailynews.com/news/national/cheap-key-promises-freedom-cops-cuffs-article-1.1363361