Do a sech on this site for your trailer. See what others are asking for their trailers.

The price of anything is always determined by what a willing buyer will pay. If you live in an area where there are not many horses. There may not be as much demand as there is in an area with lots of horses. So temper your pricing based upon what you think your local demand is vs what you see on the internet.

Trailers are worth different prices in certain area's,  Just as the person below your post stated, get on line and look at comparisons, horsetrailerworld is good, or even dreamhorse.com, then go to tack trader and do a search.  Used trailers are in a great demand right now, people are getting top dollar for their trailers.  Also call a local dealer and sent them pictures, they may be able to help you.  Good luck!