Here is a good explanation I just found; apparently the boost valve is just a modifier to the pressure regulator valve's operation, used to boost pressure under certain conditions. (Hence the name....) But the pump's output is the source of the extra pressure; i.e., the pump is the 'active device' that supplies the pressure, higher or lower, and it is just being regulated to varying pressure levels. Not sure that answered your question.
Sonnax Dodge 48RE Hydraulic Features Revealed
Now if you want really freaky pressure rises, then consider the Powerstoke injection system, that has an internal oil pump that raises injection oil pressures to over 2000 psi. In that way, the electronic solenoid has to do very little work to activate the injector; the rest of the force is supplied by that highly pressurized oil. But again, there is an 'active device' used to raise the pressure; a special pump.
