Based on this catalog, it appears to be a 1985.
https://www.ragandbone.ca/PDFs/Miyat...logue%2085.pdf
Miyata made three "Grand Touring" bicycles and this one was in the middle. The 1000 was the top model and is much coveted by those looking for a vintage tourer. But the 610 is a very nice bike in its own right.
The price seems high, but as you pointed out, there isn't as much to choose from. Supply and demand.
What I can tell you is Miyata was a good manufacturer and my Miyata 312, a 1989 model is one of my favorite bikes. I pass by lots of more expensive bikes and often choose to ride it instead.
Hope that helps.