This project seems to take its heating elements, clockwork timer and knob from a classic Dualit 2 Slice toaster - so those parts are all available off-the-shelf.
Other than that, this design needs some laser cut and bent metal, and some wooden feet. If you're able to bend the metal yourself and find some off-the-shelf feet, you could probably get the flat sheets of stainless steel laser cut and shipped for less than $100.
On the other hand, if one wanted a factory to do more demanding production processes, with more worker time or more machine setup - you're right that it would cost a good deal more.