I purchased two used Janomes (6500 and 6600) and was able to get more than I paid for them when I sold them. The 6500 was $600 and the 6600 was $800, and I got $650 and $1000 respectively. You may do better with a private sale than selling to a dealer. You just have to price it out, but I don't think you're at all unreasonable in your expectations.