445/50R16? I believe there was a typo somewhere. The only 445/50R-anything that I know of is the 445/50R22.5. The hub and brake assembly on the Sport Chassis is way to big for a 16" wheel.
As to super singles vs duals, most of the big trucks around here that were running super singles have converted to duals. The biggest reason was mentioned by firetrucker. If you have a flat and do not have the ability to change it, you are stuck on the road until a service truck can get to you. Traction is another problem. The wide profile of the 445mm tire will hydroplane on wet pavement much quicker than duals and if you happen to get into a little mud you stand a much greater chance of becoming stuck.
Yes, the cost is in the astronomical range. The tires range anywhere from $920.00 to $1050.00 each, for Bridgestone or Michelin. The wheels are around $800.00 each.
They do look cool though