Saw this posted at the evil empire, and decided to liberate it, plus do some research. Here's my take:

This was actually pretty dang cool for the time, letting a person jam along to accompanying music (not unlike karaoke) using only some... D cells to power the whole unit, I believe. Or one could simply use the tape recorder to grab guitar recordings for later playback. So-- good for quick demos, testing things out, and transcribing stuff on the fly, all in a very portable, lightweight form.

CONS:

• The built-in speaker certainly did sound like crapola.
• The neck was professional-grade, along with (arguably) the electronics, but the main body was made of thin-ish plastic that didn't exactly inspire confidence in heavy / casual usage.

PROS:

• This sucker had a fairly impressive range of all the core digital adjustments a pro would want, such as mixing levels, mixing volumes, basic effects (like whammy & overdrive), etc.
• The player was NOT actually stuck with the cheap internal speaker. The EG-5 had 1/4" (amp!) and 1/8" inputs & outputs, as well as DC power input and a couple other thangs. (see lower-right in the shot below)

Here's a magazine review:
https://www.guitarplayer.com/gear/the-plug-in-and-play-performance-of-the-casio-eg-5-cassette-guitar-was-pure-1980s-weirdness

And here's me laddie, checking it out crown-to-bum, playing it a bit:
https://www.youtube.com/watch?v=IwL2nPMIcgw

Wow, pretty neat.

Never seen this. Epic!

Until you see how much it cost.

Unless you were a Wunderkind they gave it to, 80s were weird.

WANT. For . . . uh . . . s- science?

Until you see how much it cost.

Pretty much. US$300 in ~1985.

If the main part of the head was made of maple or mahogany, then I want to say it'd be a justifiable price given all the extra features. The fact that if you accidentally dropped this sucker it might crack or shatter does not exactly inspire confidence...

At a rough guess, presuming Casio wasn't really in the guitar business, they went with a traditional strength (molding plastic pieces), and would have had to farm out the head job to an external partner, raising cost. If they'd been producing these in serious quantity, I would think that would have made more sense. *shrug*

It's almost the Boom King! https://www.youtube.com/watch?v=i3BzgsrYanQ

Lol... that would have been soooo cool if it was a decent song.

!Q@*&...

Angine de poitrine but they have to switch cassette for recorded riffs.