Also remember he didn't start with the plain glasses. Cain being Cain, he decided to start with the fancy ones. Well, why does that matter? Because the materials and processes you would use in the real world to make those glasses at minimum includes some enameling and probably silver work. Again, Cain being Cain, he likely fancied it up even further.
The layers of materials are different and they're bonded to the other materials in ways that require different types of bonds. (Okay, that's funny because what the voice dictation originally wrote was "different types of bongs." In the real world, at least for the design phase, that might not be wrong.)
So the complexity isn't just a level of care needed in creating different layers of glass or even different colors of glass, it's likely Cain trying to do the most complicated stuff ever first, as he does, and not realizing he should start with the plain water glasses.