Googling around, I came across this $5.50 part in HK: http://www.lunashops.com/goods.php?id=3508
Anyone use one before? At this price I'm tempted to order a few and test them.
Highly doubt this will give you line out, given it doesn't even has a DAC inside. The 4 soldering pad are listed as V, D+, D- and G, which means voltage (power), two data line and ground - and that's just USB connection. It is not a line-out adapter per se, just a standalone Lightning connector for you to solder on a USB connector + cable and turn it into a DIY Lightning cable.