NeXT wasn't Linux, but the point being made was that it would have been easy to dismiss NeXT as a "fringe" platform at the time. It is an argument for developing with platforms [and porting to them] when they may not be a priority for your end users.
It wasn't Linux but was based on mach Unix iirc. And they weren't cheap.. but they were cheaper than a similar horsepowered SGI workstation at the time, iiarc. But probably 10x the cost of a Windows machine.
