> That's an interesting question. In the late 90s, IBM had a competition in the same S/390 architecture, with Fujitsu and Hitachi mainframes. These could compete with IBM on price, so I don't think this would be a problem. It's hard to discern cause and effect here - maybe mainframes are expensive because IBM held to them and eventually became a monopoly.

I'm sure those were still really expensive though.

IIRC, IBM made a big investment to migrate to a 64-bit architecture, but none of its competitors in the mainframe space wanted to do the same.