There's no goodwill. It's a bar. They're not selling a name or a brand. They day they turn it over it is possible none of the existing customer base will return. Perhaps a few. The best you can do is equipment, inventory and perhaps demonstrate historical revenue that would be worth the risk for some folks that don't understand the business. Your personal relationship with the owners doesn't justify the inflated valuation.
Normally you take 1 year or 1.5 years' profit and that's how you calculate the value of goodwill, at least I've seen it done here like that a few times. And then you'll add in the value of inventory and equipment. I don't know the bar, but US$ 400,000 seems very high for a rented bar in Sosua. I can't imagine they make more than about US$ 100,000 a year in profit and the equipment and inventory, second-hand value, wouldn't be more than about US$ 50,000.