That's very naive. You are apparently unfamiliar with "comps" (comparable houses used to set the value of your own home). If someone is borrowing money to buy your house (and let's face it, most people are), your house is only worth what the bank is willing to loan on it. And if comparable houses start selling for less, that means the bank will loan less for your house.
Actually, I would say you are the one that is naive. Comps are used to price your house but they mean nothing if no one buys your house at that price. You can have every comp in your town saying your house is worth $1,000,000 but if no one gives you an offer at that price, your house isn't "worth" a million. You can list it for a million but if you only get offers for $500,000, THAT is what your house is worth on the open market, period. A bank goes by the appraisal, which includes comps but is not solely based on the comps for the appraised price, for how much they will lend a buyer.