https://www.techpowerup.com/reviews/Sapphire/RX_580_Nitro_Pl...
Many other aftermarket 580s are similar. For a sense of perspective here, that's roughly the same amount of power as some aftermarket 290Xs used. Or roughly 60 watts more than a GTX 1080. And that's GPU-only, not a total system load.
https://www.techpowerup.com/reviews/ASUS/R9_290X_Direct_Cu_I...
Polaris 10 is a reasonably efficient chip when you don't push it too hard. AMD - and their AIB partners - are pushing it way, way too hard in a desperate attempt to eke out a 2% win over the 1060. It isn't worth a 50% increase in TDP to get an extra 8% performance.
(and unlike the RX 480 - there is no reference RX 580 design, it's a whole bunch of these crazy juiced-up cards)