Should I trust those 5000 PSI listings on Amazon?

Be skeptical. The generic high-PSI units in this category tend to have thin review counts, and engineers and testers in the source threads (r/Tools, r/pressurewashing) point out that the physics of consumer electric motors make true 4800–5000 PSI output implausible at the listed price and flow. We discounted those listings heavily in favor of models with documented testing.