I bought chinese foot pegs on ebay and experienced a similar result. I had the bike at max lean in a corner and the peg snapped right in half under my weight. It looked the same. Lucky for me I was wearing a full race suit; my leg dragged a bit on the ground as I went off balance but I was able to recover.
I have no idea what that crap is, but it looks like the inside of the "metal" peg I had too. It's a very gritty cast material. Metal with some kind of cheap filler. Or a cheap cast filler with a coating on top of it to make it look metal. I'm glad you weren't hurt!
I bought some very cheap xs650 shocks from mikesxs.net so far and they have been great. They aren't the best, but they haven't snapped in half!
To be honest I have had bad experience with every part I tried to get extremely cheap on ebay. You know, they ones that are clearly a generic Chinese part. Even the plastic blinkers I got in the past melted under the heat of the bulb from normal usage!