1978 Honda Cb400, 18,000 miles?

I ran across a 1978 Honda cb400hawk with 18,000 miles for about $1800. I have yet to go see it, but the craigslist post states it's in excellent shape. My question is though, is 18,000 miles for a 37year old bike too low? That's about 500 miles a year? I don't know much about bikes. Is it worth the buy if it's truly in excellent shape?

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