There used to be tons of IEM knock-offs on TaoBao, and they'd have the exact same components as the real thing. I remember fake Vision Ears IEMs that even replicated the blue-and-gold wiring, as well as the
VE engraving on all the drivers.

But, now that most high-end brands use either proprietary drivers and/or proprietary acoustic solutions, it's near-impossible for those to get faked. The only ones still vulnerable are IEMs that use off-the-shelf components like the Trailli. There were quite a few Trailli replicas floating around AFAIK. Or, you have cases like the fake IE900, where they fake the shells, but the internals are nowhere
near the same.