They were expensive. Sun workstations that cost five figures were cheap compared to LispMs.
Their UI was powerful and efficient, but not easy to learn. They were designed by programmers for programmers. Their UI assumed that you were willing to invest nontrivial time and effort learning a broad palette of specialized tools.
Their system design made some pretty different assumptions about how they were going to be used, and the environment they would be used in. For example, LispMs didn't have any kind of security or memory protection. They were wide open systems.
If you would have wanted a comparable Lisp experience on a SUN workstation (large bitmap screen, large disk, software, ...) the actual price difference wasn't that much. But there were a lot of underpowered and slow SUNS, which were cheaper. But then you would better not use Allegro CL, Lucid CL or LispWorks on those. 16 or even 24 MB RAM were simply not enough and GC was fighting with the virtual memory pager...
The big cost driver at that time was memory and peripherals like disks.
The lab I worked for had slow SUN SPARCs. The idea was that you would net boot them and they would get their software from a main server. Relatively cheap. But it turned out a bit slow and clunky. People then often used their office Macs for software development, with Macintosh Common Lisp.
There was never a really cheap Lispm. The 'cheap' ones were a Mac II + TI microexplorer or the Mac II + MacIvory. But developer workstations were always expensive - Lispm or not - or underpowered.
What was also expensive was the software. I got a KEE license on a used machine I was given. I think it cost $50k. Similar Symbolics extensions for their OS could be extremely expensive. The graphics suite did cost several 10k per module (paint, model, render, tools, ...).
> a system that was so much designed for programmers was probably never going to command a very big market
Well, they could not live from developers alone. They were also looking for end users. Some of the machines were thought as delivery machines, cheaper and with less resources. There were also tools like 'firewall', which were supposed to keep users from getting in contact with the development environment (like debugger, ...).
Actually Symbolics also targeted high-end endusers, both with hardware and with software. They had to go beyond government developers - to be able to sell machines/software. There were applications that were kind of development centric, like the iCAD cad system - where one could program 3d models via Flavors extensions. But one huge area for Symbolics was the graphics market. 2d, 2.5d animation, 3d animation, paint/model/render. Much of that was used without programming. The graphics suite was mostly targeted at graphics professionals, often doing 3d visualizations for TV, cinema and games. Many TV stations had their logos animated on Symbolics machines.
It's a fair observation that you could build end-usery UIs on a LispM. The default UI was pretty programmery, but then that's true of pretty much all computers at the time they were being introduced.
I guess a more important factor is that PCs were cheap enough to create a market for friendlier UIs, and LispMs weren't.
> It's a fair observation that you could build end-usery UIs on a LispM.
Texas instruments ran the Interface Builder on their Lisp Machine, which was demoed to Steve Jobs and which then was developed into the NeXTstep interface builder.
> I guess a more important factor is that PCs were cheap enough to create a market for friendlier UIs, and LispMs weren't.
The higher-end commercial applications on the Lispm were kind of user friendly. Using something like the font editor or a graphics editor was not difficult. There was a problem that during its lifetime much of the UI landscape was under development - both in look&feel and APIs. There were even UIs on the Lispm that looked similar to Mac apps (like Plexi, a neural network toolkit).
Symbolics' Dynamic Windows GUI had some polish, which came from being used in some applications and it had seen some substantial investment in development. Where this investment was not done, applications lacked polish and remained experiments, demos, sketches, research prototypes, ...
TI also developed a more conventional UI toolkit for their Lispm.
> I guess a more important factor is that PCs were cheap enough to create a market for friendlier UIs, and LispMs weren't.
The market was small - I would guess that around 10000 machines were sold. Additionally the software was not portable to other platforms. CLIM was thought to support that - with some applications using it - but that was bound to commercial Lisp systems, some of them expensive... Generally I think the Lispm impact on other UI systems wasn't that great.
Their UI was powerful and efficient, but not easy to learn. They were designed by programmers for programmers. Their UI assumed that you were willing to invest nontrivial time and effort learning a broad palette of specialized tools.
Their system design made some pretty different assumptions about how they were going to be used, and the environment they would be used in. For example, LispMs didn't have any kind of security or memory protection. They were wide open systems.