Why won't this home sell?

[Leigh Ann Smith]

A friend of mine owns the home at 1808 Hickory Glen Rd, Knoxville, TN 37932.  It's been on the market for a very long time (well over a year, I think), and I don't believe they've ever even had an offer. I told her I would check here to see if anyone had some insight to share. My guess is that the problem is just that it's a high end house (listed at around $500K), and there are only so many buyers for a house like that.

If you are familiar with the Knoxville market, perhaps you could share your opinion.  Is it overpriced?  Is the market bad there?

Just a note...these people want to sell, but they are not what you'd consider "motivated sellers".