I've conjectured that the way I would attempt this is to use several gear pumps in series. Each pump should be capable of increasing the pressure of its outlet over its inlet by 2000 or 3000 psi.
The technical difficulties of this I am not sure about. For sure, the pump housings handling the latter stages must be extra robust to keep from simply bursting. Water is also quite low viscosity to try to pump with a gear pump, maybe another type would be better. But a piston pump would suffer extremely heavy piston ring loads on such an application and would wear out, or simply break out the ring lands in no time at all.
Extra precautions should be taken in the form of heavy steel lines, and heavy shielding in case something under high pressure springs a leak. You don't want to be cut in half with it
First you get good, then you get fast. Then grouchiness sets in.
(Note: The opinions expressed in this post are my own and are not necessarily those of CNCzone and its management)