The current mac pro? Parting out the bottom of the line, the processor SKU costs about a grand, because it's from intel's server line:

https://www.amazon.com/Intel-Xeon-W-3223-Octa-core-Processor/dp/B07ZN6M2SG

The memory is actually good, so that's likely closer to $400 than $160.

The storage, similarly, won't be a bottom-of-the-line stick of M2 you can just go buy. Enterprise storage costs a fortune.

The GPU / motherboard / etc actually involve custom work from apple. In particular the GPU doesn't just use PCI-E, it has a higher-bandwidth slot. Sure apple will sell you one for $700, but the other half of that equation costs money too.

They're premium, but the build quality is high, and sometimes that's actually what matters.