That 50 watts only happens under a fully-loaded PSU scenario. 500w PSU at full load would deliver at 80+ rating ~400w. That same PSU just rolling barely enough

That 50 watts only happens under a fully-loaded PSU scenario. 500w PSU at full load would deliver at 80+ rating ~400w. That same PSU just rolling barely enough equipment to keep a processor fully fed might draw 300w from the PSU, of which maybe 20w of that is wasted. This is basic PSU and power supply principle.