Before shitting too much on current workstation designs, check how much an SGI workstation would cost back then. Onyx started at 100k USD in 2000's money without adjusting for inflation. For that kind of cheese, they'd better be designed by Gucci.
But an onyx wasn't really a "workstation" anymore. The one we had at work required a 3-phase plug to support all the rendering pipes. Mini-super-computer would probably best define it
I'd say it's more about fashion than cost. I bet Apple spends more on designing and manufacturing their computers than SGI spent on their moulded plastic trim, it's just that the fashion these days is incredibly boring and lacking in imagination.
The cost of an SGI wasn't the plastic trim. They were loaded with a lot of custom chips that were all relatively low production volume. Those components had a relatively high cost because of the production volume and then obviously a nice margin added on top. The plastic exterior was literally just decoration.
