Electrobrand is not common, might even say pretty rare. Pretty sure the guy wants lots of money because it comes with a carton. I do recall seeing one example sell a couple years ago for what I considered at the time, suprisingly high although I don't recall the exact amount, just seemed high to me.
Personally, I would not buy it for $500. That's 1/2 of a decent M90 already and this isn't nearly 1/2 of an M90 in terms of quality, sound, respect, prowess, etc.