80 hours is press time. Any normal gamer can shave 30-40 off of that. People said P4 was 80 and it's really more like 40-50 for any normal run.
Did you play on easy and ignore everything besides the main plot? No way those games are only 30-40 hours unless you're trying to intentionally hurry through it.
Here are the average completion times for Persona 3/Fes/Portable, Persona 4/Golden on how long to beat, without extras and just doing the main story.
Persona 3: ~84 hours
Persona 3 FES: ~80 hours and 30 minutes.
Persona 3 Portable: 68 hours and 30 minutes.
Persona 4: ~73 hours.
Persona 4 Golden: ~70 hours.
As you can see all of these are almost 80 hours except P3P, which makes sense because they removed anime cutscenes and 3D world exploration from that game, and as such it's more of a Visual Novel with point and click interface and 3D dungeons. I don't think it's feasible to beat console versions of P3/P4 and shortly, P5 in 50 hours unless you're intentionally skipping text/scenes/etc.