For me, THE big plus about the smoke lens (not tried other Darkstorm lenses) is the VFD readability in high ambient light situations compared to the 'stock' lenses - the improvement is worth the money easily.

If I wanted to pretend to be an accountant I would say something like "that $20 lens allows me to view the display on my $1000 player approx. 20% more than I could before the upgrade".
Perhaps someone better than I could express this more scientifically (say) in cents per (useable) lumen?