so how do you know what they use?
No one does, it's a trade secret. A secret most other manufacturers only do minimal work, if any to hide. For instance, using branded OEM caps. You can't tell if they are expensive or cheap and you can't buy them yourself.
I should point out not all speaker makers use cheapest possible parts or go through any more trouble than putting crossover components in the speakers.
B&W uses Mundorf in some speakers, as does Magico and Joseph.