Small data points. A few years ago as an AA Gold, I was upgraded from paid PE to J on BA MIA-LHR. I was flying solo, and it was busy summer travel so my best guess is they were oversold and already rolled up higher tier elites on BA and AA. I was kind of looking forward to the new PE seating, but the cramped J lie flat seat (luckily a forward facing one) was fine for the ~8 hour trip.
Me too. A few years ago, I was upgraded 2 out of 2 times to Business when I booked PE on BA from LAS as AA PLT, due to oversells in Economy moving people into PE
I wouldn't pay the $480 extra for that flight, but some people have more extra money than I do.
I did pay $46 more for a 789 flight DFW-LAX to get PE seating on an economy fare, and also because it was a good time......which is why it was more than other economy on some flights,,but still less than others