More aptly, FPU and MMU hardware were incredibly expensive in the late 1980's and early 1990's, and the amount of RAM to sustain running A/UX would've crept you

More aptly, FPU and MMU hardware were incredibly expensive in the late 1980's and early 1990's, and the amount of RAM to sustain running A/UX would've crept you closer into workstation territory anyway. Keep in mind that this was a time when one was not guaranteed to have memory segmentation hardware, let alone floating point hardware. We take this for granted in 2015, but in the period between 1985 and 1995, it was a serious luxury for lots of computer buyers. That said, with 4MB of 60ns RAM and a 68030 costing you $10k to start on a Mac IIfx and an upgrade to take you up to 8MB potentially costing you another couple grand, why not just go SGI and be done with it?