A fair price is the amount at which the asset could be bought or sold in a current transaction between willing parties. What an item sold for in the past or will sell for in the future may not matter. Since we are not your potential buyers we should not determine what is fair for someone else. If you consider us your potential buyer you're in the wrong forum. Why not list it in for sale or trade and see what you get? You can list it for any price you want and if you find a buyer that is willing to pay you price all is fair.
I think what you are doing is telling a lot of potential customers you have a stringing machine that you would be willing to sell.
I have the ability to drive people crazy, not sure if I was born with it or I learned it but I'm damn good at it.