A famous version of this was the "Pepsi challenge". It turns out that people preferred the taste of pepsi in the test conditions, but coke in other, longer testing conditions. So part of it is biochemical (e.g. the taste you experience on the first bite/sip of something is not the same as the 20th) but some is also mental. Your experience of the taste of something can change with the environment you sample it in.
The question at hand is whether a cheap/expensive wine, of the same type, would matter in the boar stew example.
Personally, I have no reason to believe that a more expensive wine would only shine under these types of conditions. I also think it's a matter of subjective taste, and there is no arguing matters of taste ;).
From the non-oenophile POV, my objection is the pretension of objectivity. "This wine is better than the other one" is a subjective statement masquerading as an objective one.
That's how it is for most everyone, I think the disconnect is that the newbie isn't aware of that and make take the "expert's" opinion out of context or too serious. And the experts can be jerks too, but I think it's more people unfamiliar with wine seem to come into contact with the jerks first for some reason and wine gets a bad knock because of that.