Indeed... basket casting machines cost millions of dollars so there aren't a ton of companies doing it.
There are two HUGE companies that make the majority of bulk cast baskets (I visited both -- including the one from Russ's video) -- and a third, smaller, but still good size company that is doing most of the new tooled stuff... they do mine, DD's, Skar's, Ground Zero, new Orion frames, and several others that I saw.
Cones are largely from the two big guys as well... tons of places make spiders... there are several good quality coil factories (4 good ones that I have experience with) and a ton of low quality ones.
But -- in the end -- the loudspeaker business, aside from tiny speakers built into electronics, isn't a terribly big business... I mean the enthusiast level "big" stuff... so only so many places are going to make the parts.
The key is... asking for & being willing to PAY for good quality parts and QC checking stuff.