Retail cost is $19, but I usually get them from vendors on eBay. I usually pay about $7 to $8. Be sure to get the Apple ones...the knockoff ones don't work and may mess up your Lighting jack. If it costs less than $7, it is likely a non-Apple adapter. How to tell the difference...
The best feature of these is that they don't wear out like the traditional Apple Lightning cables. If the cable gets damaged, swap it out for another. The biggest problem is losing the adapter -- it is quite small. I usually leave it on a cable. Using a short (less than 6 inch) cable makes it very compact.
These are especially nice for folks that need a Lightning cable and a regular Micro USB cable.
