Unfair pricing of an apartment

I have a neighbor who is a yeshivah student. He’s trying to sell his apartment, and now he’s in the middle of negotiations with a potential buyer. The problem is that this apartment is really terrible! The truth is that the seller didn’t withhold any information from the buyer. But because the buyer is not local and doesn’t really understand the local market, he is, in my opinion, about to agree to pay a price that is completely exorbitant. When he realizes that, he’ll be very, very upset. So, my question is as follows. On the one hand, I’m all for the seller getting the best possible price for his apartment. On the other hand, I feel sorry for the buyer, who’s about to experience a major loss. Do I have to tell the buyer that this deal is no good? Or maybe I should only disclose this if he asks me on his own? Or should I avoid telling him even he does ask me himself?  

You should ask a professional realtor, whether it’s realistic to sell such an apartment for such a price. If he says that the price is very high as compared to the market price of such apartments, that it’s completely exorbitant, only then should you notify the buyer.