This is one of the rarer specific Apple II models (happens to also be the fastest and the last released). They’re maybe $300+ or so in good shape. The more common Apple IIe goes for significantly less. I bought one for $50 4 or 5 years ago.
Weird to hear it described as "rare" because it was the only Apple that I had as a kid, but there were a _lot_ of Apple IIe/II+ around at the time. (I remember that we had a 300 baud modem, actual Bell equipment, hooked up to it.)
Still the IIgs might be more rare? I seem to recall the world had moved on by the time that came out.
Are you sure you had a IIc+ and not just a regular IIc? The easiest difference to notice is that the IIc+ has a 3.5" floppy drive, while the IIc has a 5.25" drive. The IIc+ came out in 1988, as opposed to 1984 for the IIc.
I don't have hard data of course, but I've been an avid Apple II and Mac hobbyist for a while, and own every model of Apple II. I think the only Apple II model that's rarer than the IIc+ is the original II, and that might not even be true. (The original II is _definitely_ more expensive, but I assume demand is also much higher.)
The IIgs is pretty easy to come by. It came out two years before the IIc+ and was also on sale for a lot longer than the IIc+. The IIe is definitely the most common. It was in production and on sale for 11 years, and schools bought tons of them.
There were a lot of IIGS's, schools purchased them in bulk. Plus, they were the machine to upgrade to, so a lot of die hard apple ][ users ended up on the GS.
The IIc+ is actually the last apple II created and wasn't particularly popular because it "split" the market by being a 8 bit computer which couldn't run the newer IIGS's/16-bit software. OTOH, it was clocked faster than the IIGS. In a way it was just apple's response to the laser 128+, which was a much better IIc. The cynical take was that apple didn't want to create another product that would eat into its mac sales like a 32-bit apple II, or much faster IIGS would have done. So they backed the feature set down.
The IIGS continued on as the choice apple product long after the IIc+ came out because people were just buying transwarps/etc, hard drives, etc to create a more advanced IIGS.
Commodore's response to the IIGS was to make the Commodore 65 an upgraded Commodore 64 with Amiga style graphics and sound. It never came out. There is a clone at http://mega65.org/ that tries to complete the Commodore 65 with a 50Mhz CPU. Something about the 6502 not being able to be clocked more than 25Mhz prevented it so they made the 4502 that can go up to 50Mhz.
I grew up on the IIgs at school. I can only imagine that there were millions of them. They were certainly outdated at the time; I think I had a Performa 6112CD (PPC 601) at home during the era those were in my school.
(I might be mixing up the eras a little. I most remember the Performa but that was the next computer after my 386, to which we upgraded from a Tandy 1000. I still remember writing my first program on the Tandy.)
