I'm pretty sure they would be more expensive than 19 dollars if they were sheepskin. I'm also fairly sure that sheep don't have straight, plastic hair. I like uggs because they are quite cozy.
I took this straight out of Wikipedia because it's late and I didn't wanna rewrite it. "However, similar to the sourcing of leather, sheep-skin is a by-product of processing sheep for human consumption; sheep are not killed for their skins. Because it is a by-product, the supply of sheep-skin is limited by the number of sheep processed for the meat industry. The rise in the popularity of Ugg boots has been the "driving force" in recent shortages, which have seen sheep-skin prices from 2010 to 2012 increase by up to 80%."
- Liam Nesson The grey