You didn't prove much. You have to be in the right state of mind to appreciate subtle things in wine. If you aren't paying attention to it (eg, you are at a party and not a wine tasting event), you'll miss it.

Just because nobody could tell the difference doesn't mean the cheaper wines were the same as the expensive wines. It just means you served expensive wine at a party where nobody was expecting to have to put effort into analyzing their wine.

Lets not even forget that some of these folks could have a been a few drinks in already...