To USB you mean? The cheap ones only do 10gbps, not even a quarter of the speed a PCIe4 drive is capable of. 40gbps adapters are up in the ~$100 range.
Oh, that type of adapter. Those work but they'll only fit in the Mac Pro, which has a $3000 premium over a Mac Studio with exactly the same specs, so you're unlikely to come out ahead there.
Sorry, I realized I misread your previous comment. I thought you were saying the markup on a PCIe drive for the Mac Pro was too high. Now I understand you were referring to the markup on the Mac Pro itself.
[0] https://www.amazon.com/M-2-Adapter-Aluminum-Heatsink-Solutio...