Ok, for those of us who didn't get the email. Which casters are you referring to? I went to their web site and they have lots of them starting about $7 for 1k load rating for a swivel w/ brake and roller/ball bearings, but a phenolic wheel. To me, phenolic means the old WW2 bakelite stuff that was used to mold all kinds of things. It's pretty durable but brittle.
on edit: Never mind, I think I found what y'all are refering to. It's the 1050# swivel with a green poly tread. That looks really good, I will probably order some myself for implement dollies.