My unscientific observation has been that the opposite holds for French wine. They seem to ship the US their worst, but it hits our shelves marked up 4x what it'd be in France.

Maybe it's a branding thing, and French wine's got enough power in that department that they don't need to send us good stuff to move product, at least at the lower end. Maybe with some French writing on the label low-price-shopping consumers are equally likely to buy it whether or not it tastes good, so there's no reason to send anything but the worst they have. Other European countries seem to have no trouble shipping us nice wine in the lower price tiers, but then they're not France.