Having a buyer's agent DOESN'T cost you anything. It costs the seller. You are still paying the price that you want for a house. I.e. You can offer $197k without an agent. But that doesn't mean you have to offer $200k with an agent. You can, and most likely will, offer $197k in both cases.
I would say that in general, a buyer is going to more or less pay the same price with our without an agent. But of course there will be exceptions like your example that certainly will happen.
If I'm a buyer and I've offered $200K through a realtor, but another prospective buyer has offered $197K without a realtor, who do you think the seller is going to sell the house to?
THAT is where it "costs" you something as a buyer.