Attention rich people who demand high-quality audio performance! Italian designer Andrea Pivetta has created the Pivetta Opera Only, a $2.2 million marvel that is almost certainly the most expensive amp in the world.
Pivetta advertises his Opera Only as a "unique crossing between sophisticated technology and art"; the amplifier resembles an enormous, 12-sided Mac Pro (and or black trashcan), and opens up when in use, like so:
The amp weighs 1500 kilograms, or a shade over 3,300 pounds, and is a little over 8 feet tall.
You can read more about the Pivetta Opera Only at Andrea Pivetta's website (which features some truly soaring prose, at one point comparing the opening of the Opera Only to witnessing the rise of the Phoenix.)