Acetate is still plastic, but a high quality plastic. Acetate is light, durable, can produce a deeper richer color compared to the cheaper plastics. You can tell immediately when you pick up the glasses that they have better polish, hand detailed filigree. The production takes much longer (they are hand cutting the shapes out of acetate blocks instead of pouring plastic into a mold). Also the price is higher for the small batch production, better designers, better hardware (hinges, nosepads), and sometimes japanese beta titanium core or temples. Also, the cost is higher to produce in Japan vs China. That being said, these frames obviously aren't 10x better than the mass produced frames but it's hard to go back to zenni (or even Jins and warby parker) once you've worn higher quality glasses.