One thing missing from the comparison to IBM and Sun is that precisely because those companies made things so expensive people
started looking for alternatives.
The ES/9000's were really good machines for the time. Had IBM not raped people on those, companies might have stuck with them for a little longer. The AS/400 was priced more reasonably and people loved those. You couldn't get someone with an AS/400 to move to a Unix workstation if you used a nuclear bomb.
As for Sun in 2001, the problem was that they were so absurdly overpriced and underpowered that commodity x86 simply blew it away. If I didn't have direct knowledge of the dysfunction that was Sun at the time, you would have thought they were taking kickbacks from Oracle, Cadence, Synopsys, etc. to limit performance. (Explanation: Oracle, Cadence, Synopsys, etc. all had very expensive software packages that were licensed per processor core per year and effectively only ran on Sparc. So, the lower the performance of the processor, the more cores you needed and the more expensive your license to Oracle, et al.)