Mike,
The Wood River casters are indeed made in China. I don't know where the Carrymaster (Zambus) casters are made. From what I can tell the Carrymaster casters would be about $200/set with 1300 lb capacity. I found several places that sell Carrymaster, but didn't want to hassle with calling and ordering (couldn't find any online stores that carried them). I've seen the Foot Master casters, but the only ones I could find were either too small capacity (480 lbs with 4) or as expensive as the Carrymasters ($240/4 with 2400 lb rating).
The Wood River casters seem pretty high quality, and were the lowest priced caster of that type I could find. Of course 2 days after I placed the order from Woodcraft I see two other Amazon sites with the same caster set for $30 less.
Evan
Carrymaster and Foot Master casters are both made in Korea. Both are good but I prefer the Carrymaster brand. I had Footmasters under my mill and didn't like the screws for the levelers - seemed flimsy for the rating. I took them off and installed Carrymasters and they are stout for their rating. I can push an 800# machine around my shop with one finger and then ground and level it in a few minutes. The leveling feature is solid, unlike the Foot Masters, and it doesn't change over time so I'm going with Carrymaster from now on.
I actually switched the Foot Masters to go under my lathe but I just don't care for the feel or solidity of the leveling feet so they're being replaced with Carrymaster AC-600's. The AC-600's weigh about 3# apiece and they are massive. I chose them because I don't want flex or movement under a lathe and I know the AC-600's are stout; I have two of them now and am waiting for a better price on the other two (got my two from Amazon for $20.00 each, shipped!)
I saw the Wood River casters and suspect they will be fine provided the rating is at least double the weight of the machine. You sure cannot beat the cost. I didn't go for them because I didn't want to chance a mishap or breakage with a heavy machine sitting on them but I admit that I'm probably being overly cautious about that. The wood shop guys seemed to think well of them.