Unfortunately with the economy the way it is right now, horses are completely a buyers market.
For $2300 someone can get a nice young Thoroughbred, or a nice show horse that someone may need to just get rid of quickly.
Your horse is 17 years old this year, right?
Unfortunately, I can pressume that that is one factor that is deterring buyers from your horse at this price. Most people assume (Not what I believe, but it is how many people think) that a Thoroughbred at that age is going to have leg/joint issues, due to racing and the wear/tear over the years. When they can get a younger Thoroughbred or possibly a young off-the-track project for that much or less.
Lowering the price would probably get you more inquiries. Hate to say it, but in these times its true.