Used to have this JDM machine. Top of the range back in the day, yes. Came with a wired mike with remote controls on it.
I've got an 8290, for 1980 these were very modern looking and they've aged extremely well. The dual antennas are so nice, they look much better than single antennas. You don't see too many wired remotes from back then, these would have been some of the first to have any remote.
I'm not sure. I suspect probably about $600, considering that the M70 was usually around $400, judging by the sales receipts I've seen.
This may have been the king of the hill back then, at least price-wise. Hitachi is another company that makes a ton of other products, it looks like it started a long time ago with electric motorss.
Here in the UK the only new Hitachi products we see are large excavators and trains https://en.wikipedia.org/wiki/British_Rail_Class_395 they claim to make TVs, even having a picture of the train on the box but the TVs are actually Vestel.