Whenever you are trying to determine price on something used, I recommend finding how much it was new online and then figuring out a fair used price. Another option is that I recommend going onto a sight like craigslist or ebay and see what other people are selling comparable items for.
If it will not function without a remote and you dont have it then you may have to be more flexible on price, as remote controls run in the ballpark of $25 to $40+. I would probably just sell it as is. The Home Depot does sell remotes for ceiling fans.