That is accurate.
There's a few hurdles with making waterballs that actually add to the price... One is that they're Perfect Circle shells. If Perfect Circle fills them, then they're 50 cents a ball off the bat for a batch. If RAP4 fills them, or chinese slave labor fills them, it's a complex process to do manually... Each side of the shell has to be solvent glued together.
And, like jk6109 said, the market is still there at that ridiculous price. Bullets for range practice aren't that much cheaper.