Wine gets expensive at the higher end because of supply and demand. They don't make many cases of a wine that costs $250/bottle obviously. And some become a "thing to have to show off, not to drink", like Screaming Eagle or Petrus or a DRC. My taste buds don't discern much difference between an $80 bottle and a $250 bottle in terms of the latter being clearly better, it's probably different.
I think around $30 retail one can get a pretty good bottle of whatever, probably notably better than a $12. Maybe at $60 it's better than $30, but the difference, to me, starts to shrink for that extra $30. I don't mind having a $60 every so often, usually in our case it would be champagne (which I'm not that crazy about).
And of course expensive wines include dropping fruit, limited acreage, dry harvesting conditions, care sorting and fermenting, usually longer aging probably in more expensive oak barrels using a more expensive cork (which can cost $2 each in somce cases). But a lot is just cache, I think.
