It's cheap because it's 10% cypress, at least 50% pine, and the rest is a mix of other hardwoods, which can include cedar and black walnut depending on what was being milled that week. I called the company that makes it and asked.
I've used Repti-Bark and found it dusty and expensive. The dust settles to the bottom of the enclosure.
I'm currently using cypress from Reptile Basics ($25 for 2 cu ft shipped) and am very pleased with how well it holds humidity, is soft, and not dusty.