Unless they are ordering direct, then REDG doesn't get money from the retailer, they get it from Diamond the distributor.
As I understand it from my comic retail days working in a shop, comics publishers get approx 40% of cover price. So on a $3.99 book REDG would make $1.60 if that is still true.
Retailers make (depending on how many they order 50-55% (or used to). So even if selling at 50% discount they would likely still make 5% plus any shipping and handling markup they include to pad things.
But I am guessing Westfield does this promo for a loss leader to get new customers and take a tax deduction to offset. So they don't really lose out.