I think you're mixing up cycling functional threshold power and VO2 Max. FTP is usually defined as maximum average power output that can be sustained over a solid hour. Usually only top male pros can get over 400 W, and 500 W might not even be physiologically possible (at least not without doping). Of course many strong riders can hit over 500 W for shorter efforts.

VO2 Max is the maximum amount of oxygen that someone can metabolize measured. The highest measured VO2 Max scores are about 96 ml/min/kg. No one can sustain a true VO2 Max effort for more than about 10 minutes, and there is only a loose correlation with FTP.