For purely acoustic music sub-40Hz content is rare, but for any modern music with synthesizers like jazz or popular music, there's a surprising amount of deep bass content
Right.
The lowest note on a piano is 27.5Hz. The lowest note on a 4-string bass is 30.8Hz.
In my pedestrian opinion, those notes are not the "most" often used notes in any music. If I'm putting together a system for music, I want the "most" used frequencies to be good first. Then as the budget allows, expand to the notes that are less frequent.
Even in the examples you give, look within a song. "Most" of the music is not in the subwoofer range.
Another point. Say you have good mains and a good subwoofer. The designer of the mains is far more capable designing crossovers than I am by setting 40/60/80Hz in my AVR. If my mains are capable, I would rather fully use the crossovers designed by the speaker designer for accurate music. If I want to artificially boost the bass, I can inject the subs and crank 'em up. It is a fun capability, but not one that I use "most" of the time.
If I'm building a system for music, I will focus on the things it will do "most" of the time, then consider the rest. With a $500 budget, that means Mains.
