How much is a complete Marx 3987 12 train set with box worth?

The value of a complete Marx 3987 12 train set with its original box can vary significantly based on its condition, completeness, and market demand. Generally, such sets can range from $100 to $300 or more, with pristine or well-maintained examples commanding higher prices. For an accurate valuation, it's advisable to consult recent sales or auction listings specific to Marx trains.