Best place to buy six foot PVC caging?

[Wh00h0069]

http://www.animalplastics.com/ T20 (72L x 24D x 24H) terrestrial cage $440

I saw that, but I wouldn't pay that much. I was able to buy two four foot cages for $350 shipped, brand new. I don't understand why six foot cages cost so much more than four foot cages.