[ora600]

Except that sometimes differences only exist on a slightly more expensive scale.

If you can't tell the difference between 6$ Cab and 6$ Merlot, it is likely because at this price range there is very little difference. Better wines are better at expressing the differences between the grapes. Cheap wines are all fruity and alcoholic.

[gnaritas]

And yet taste tests show that even experts can't tell the different between the good stuff and cheap stuff they're told is the good stuff because expectation plays more of a role in what they perceive than taste does.

[dtegart]

Master's of Wine certainly can. Quality is part of the test, as is the ability to tell variety and region. From http://www.mastersofwine.org/en/examination/index.cfm Practical - three twelve-wine blind tastings, each lasting two and a quarter hours, in which wines must be assessed for variety, origin, winemaking, quality and style.

[runjake]

This is the argument that Monster Cable* uses.

* Monster Cable, please don't sue me.