I design parts and machines for a living. A flat sheet of plastic cut to size is about as low effort as it gets manufacturing wise, and can be easily sourced for reasonable prices from a large number of shops at the volumes he's probably making them at. There's no tooling costs (except maybe some hold down fixturing for post processing) and little in the way of skilled labor for making the parts.
As for expensive equipment, if you want to bring it in house, you can easily cut 3mm polycarbonate on a cnc router, which can be had for 5-15k depending on quality. I'm not saying that's not a big expenditure for an individual, but it's peanuts in the world of manufacturing.
Three dimensional molded parts or carbon layup parts require expensive tools (especially with the fairly large geometry - we're talking easily 50k in tooling in China, double that in the US at best), and carbon layup parts also require a fair amount of skill to get quality parts.
Don't get me wrong - I think it's a cool and very clever solution, I just think the price is really steep considering the competition.