The point was that, price of simple bread was government-regulated, so producing and selling it lost money to bakers and they either didn't do that at all when they could get away with it, or only did in minimum quantities that got quickly sold out. Prices of brioche, as a higher grade product, were not regulated, and brioche was always available.
So really, that comment was more of pun illustrating how lame government price control policies were, rather than an indication of lack of touch with ordinary people's lives.
And ultimately, that common reading is what is being referred to in the comment that spurred this thread. Regardless of the historical minutiae regarding the quote, it's making reference to the anger of a country's people when the cost of living rises and is perceived to be met with indifference.
Also she was 10 years old at the time, which actually makes it even more likely for her to blurt out something like this. Children are quite naive as I think we all know.
I've read other articles on the topic and emerged unconvinced from them as well because the crux of their "evidence" was basically "a wide consensus". Hrm. "A wide consensus" amongst a small group of scientists where deviating from the accepted opinions of the majority bears an existential threat to one's entire life work and career is... shall we say, not convincing.
She wasn't 10 years old at the time. Born in 1755, Marie Antoinette would have been ~34 in 1789. Or are you talking about someone else?