Oh no, here we go deviating from the subject…
It’s usually very obvious if the helmet has suffered structural damage. The paint will chip/blister/bubble if it has suffered an impact severe enough to damage the fiberglass. If the foam is EPS, it will also show some serious compression damage from an impact of that magnitude.
My opinion on the subject is that if they don’t exhibit any of the above, just cosmetic scratches, I have bigger things to worry about while riding.
Besides, I feel much safer in my lightweight, comfortable, ventilated, quiet (scratched-up, $100 used) $700 retail Arai than I would in a heavier, uncomfortable, hot, noisy, no-name…but pretty, $100 new China brand that I might decide not to wear. Phew.
But that’s just my opinion.
Russ