Hard to say on that one without seeing a list of what they have. Some rare corals or fish are worth big money and I've seen SW tanks easily top that. More than likely like not and he's overhyping it but it's possible it is worth it. Also depends on lights on the tank, etc. Cheapo fixture could be $150, high tech ones can be $1000 alone.
A list would help though. It's like someone posting a shrimp tank with over 100 shrimp in it for sale. 100 cherries, maybe $100 worth of shrimp. 100 Taiwan Bee's, $4000 in shrimp. lol.