"This company" (Parsons Xtreme Golf = PXG) was started by Bob Parsons - founder of GoDaddy - a few years ago. His goal was to build the best performing, most technologically advanced set of golf clubs in the world, no matter how much they cost to design or make. He hired a bunch of top designers in the industry, gave them a blank slate and a blank check and told them to go to work.
The heads are definitely unique, using a variety of materials such as a forged carbon steel body, maraging steel face, tungsten weights, and the hollow body is filled with TPE (Thermoplastic Elastomer...basically synthetic rubber, LOL). I'm sure the cost to manufacture the heads is fairly high due to the complexity compared to a standard forged or cast club, and if the cost is 4-5x as much to make the heads then that would justify the asking price of 4-5x of what a typical high-end set of irons sells for. But as a golfer, you certainly aren't going to see a 4-5x improvement in your game by buying them. They're nice, don't get me wrong, but your money would be just as well spent on any other properly fitted set of irons out there.