SpaceX crushes rocket engine world record during Raptor test

There is problem to reach it for this amount of fuel using the same amount of fuel as energy source. The flow is fixed, so pressure is proportional to pump power, which is a part of turbine power, which takes energy from that fixed flow. To get more energy, bigger temperatures are needed - on both fuel-rich and oxidizer-rich turbines, and that's limited by existing materials.

Of course, there are many complexities with efficiencies, balances (spinning, two turbopumps), thermal expansions and contractions (LOX is about 90K), cooling of turbine blades, if any, control of pressure feedbacks (e.g. the bigger power on turbine - the bigger pressure on pumps, which supplies fuel to gas generator and then to turbine, so we have a positive reinforcement loop here)... No, the problem isn't the pressure - it's the pressure given all the constraints of the leading edge rocket engine.