Bulk discounts don't "penalize" smaller purchases, they reward larger purchases.
Companies offer bulk discounts on basically... everything.
This is like pointing out that the Dollar Store penalizes people for buying small quantities and thus suggesting that Costco should raise prices to "make it fair".
No, it is discrimination based on marital/family status.
If they were willing to sell me 5 flight coupons for a discount, that would be acceptable. There is nothing I can do as an individual to take advantage of the discount.
