I suspect that because he ran his robotic hair cutter off of a Teensy, he probably uses it on a bunch of his projects. He explicitly called it out in this video.
Interesting project. I can't imagine the time invested in building that chitty-chitty-bang-bang like contraption. However, given his views, I'll guess he is getting around $8/1000 views so 4.4 million views = ~35K. Dang...what am I doing wrong?!?