Just the cart in okay condition, probably like $10. if you have everything (manual, map, sleeve) like probably $30-$40. Just depends on the collector. There's probably not many "serious" Nintendo collectors without a copy of this game.
That sounds about right. If there weren't a hundred ways to obtain a copy of this game then it'd probably be worth a lot more. But at this point, all you'd really be getting is gold plastic.