[zimzam]

I think this is a framing issue.

Is it fair to charge people with different sized families different prices (per unit) for toilet paper?

vs.

Is it fair to charge people different prices (per unit) for different sized packages of toilet paper?

The former makes it seem nefarious but the latter is commonly accepted as fair. Same for airline tickets - if there's a discount for buying in bulk that's just as fair as a discount for buying toilet paper in bulk.