I personally don't care if I know or not. And I rarely know. Correctly pricing your domains is vital. If done correctly, who the buyer is won't matter too much. Even with Make Offer, it doesn't matter to me if I know.
Certainly I try to find out, but mostly I just know what I want for domains. I don't really try to set prices based on the buyers financial position.
Could you imagine being charged more for something just because you pulled up in an expensive car?
Cheaper for the people that drive old beaters, and more for people that drive nice cars?
It really doesn't matter to me usually.