I can also see why people go grey and it can make sense but people shouldn't be deluded into thinking the savings don't largely come from tax fraud and other business practices that are unsavory, e.g. Splitting lens kits , selling lightly used refurbs as new. It certainly isn't the case that they simply lower their margins, margins are already low.l which is why high street stores struggle.
I'm struggling to see how splitting lens kits is "unsavory", I think everyone realises it's tax fraud, but not following big brothers tax rules doesn't make it immoral.