Bordeaux is an enormous wine region producing more wine than most countries, but it's not all expensive. You can find lots of Bordeaux for $10 or so; I'm drinking one that cost $14 as I write: Chateau Timberlay - research for a story about wine in Canada in the 1970s. But Bordeaux is also the epicentre of the world's fine wine trade. 

In addition to the Classification of 1855 wines, including the most august chateaux like Lafite, Mouton, Latour, Margaux and Haut Brion, there are even more highly valued wines like Le Pin, Petrus and Chateau d'Yquem. Having tasted many vintages of these wines - like the amazing 82s of all of them (except Le Pin) and the stellar 1970 Chateau Latour - I think Bordeaux rules. But so do a lot of other people. During the lengthy 90s/00s boom that has now sadly ended, a lot of very rich people insisted on having these wines, of which there are very limited quantities. 

Not Just a Bit Torrent
Market forces mean that the sudden torrent of cash caused both the prices and the price differential ratios of the top marques vs. either other Bordeaux or other top regions to go through the roof. Recent futures prices are both understandable and completely ridiculous, thanks to flashy show-offs and, to a lesser extent, speculators who live in free markets (i.e., most other rich countries) and hope to sell the wines for a profit in a few years. 

The chickens have now come home to roost and it looks like the people who don't really love the wines have flown the coop. While that's rough on the business models of the top producers, used to years of double digit price increases, I have no fear that the bordelais will stop making the world's best wines. 

Lemons/Lemonade
Wine lovers can cautiously hope that the better Bordeaux will revert to "extremely expensive" after several years of "beyond ludicrous". 

Check this downbeat Decanter story for an update.