There are a lot of speculators like him, who are invariably buying to let.
His interest is purely confined to the maths, he will only pay the price that works for him and he watches the area's house prices over time and probably has estate agents passing him information.
If he sees 2 price drops on a particular house then he knows the seller is not "waiting for the market" and makes his offer. He is not interested in any higher price, he will just offer on another property.
Of course a house is worth what it sells for, not what people ask for. The other houses haven't sold because their price is higher than what local buyers are prepared to pay.
You claim a "loss", but unless you paid more for it than this offer, then it is loss of expectation, not money.
So you can either deal in today's market, or wait until it moves up to your expectation with no guarantee that it will.