I think it would be more accurate to say the RISC workstation built entirely of custom low volume components was a dead end. Even if SGI decided to cut their margins to compete on cost their lowest prices would still be way above a PC workstation. Compaq benefitted from economies of scale that SGI could not.
RISC architectures live on today. Your house likely has dozens of MIPS chips in various components. You've got more ARM chips for sure but no shortage of other RISC chips in various components.
“Custom low volume components” is a marketing strategy. They could sell them to competitors and make money off the components. Late in its history SGI owned MIPS and sold their hardware to others. I have a WindowsCE laptop running on a MIPS R4000 processor. Runs NetBSD with effort, but with dignity.
RISC architectures live on today. Your house likely has dozens of MIPS chips in various components. You've got more ARM chips for sure but no shortage of other RISC chips in various components.