The original version of NS for PC (3.1) required 16MB RAM and recommended 24 (32 in 3.2). The software itself cost $800. In 1993-94 there was a massive RAM shortage caused by a factory fire in Taiwan. RAM spiked to over $50/meg. The additional RAM to run NS alone would have been worth on the order of $1000 even in 1995 by which time prices had gone down.

All told, a NS system would cost around 3x the cost of a Windows system.

Yes, this is all true if I'd said 'NS 3.x as it was then, developed by Next, could have been a drop-in replacement for Win 95'. Which I didn't.

No way. Even if Microsoft had been prepared to throw out Windows 3.1 and DOS compatibility (or engineer it in at substantial expense), NeXTStep would never have run acceptably on the low-end target machines.

It was a decade after the '95 release before optimization and hardware advancement had a NeXTStep-derived OS running 'snappily' on consumer desktops.

Nextstep ran on 68030s. Had it been a Microsoft product (since the late 80s) there's nothing inherent in it that couldn't have made it a consumer OS by 1995.

I think one of the problems is the RAM prices back then, which also affected Windows NT sales. 4Mbit DRAM chips was for example costing more than $10 a piece.

That's true but the original Next machine shipped with 8 megs which by 1995 was the recommended amount for Windows 95. There are lots of reasons Nextstep was a commercial failure, I just don't think 'hardware requirements' is fundamentally very high on the list. 1995 was just at the beginning of a rapid decline in DRAM prices, to boot.

MS spent a lot of effort trying to fit Win95 into 4 megs for a reason. I don't think NeXTStep with only 8 megs were a popular configuration, many was upgraded to 16 megs.

Win95 didn't fit in 4 megs all that well. But that's neither here nor there since we're in a parallel universe in which MS started working on Nextstep in 1985 and released a consumer OS based on it in 1995. This seems totally plausible. Next Inc was never really making a consumer OS. In 2007, Apple shipped a Nextstep derivative that ran in 128 megs while its desktop (and consumer) counterpart wasn't really happy with anything less than a couple of gigs.