This cartoon by Gary Barker from The Sun relates to the record-breaking post-Christmas sales in the UK.
The joke is that the two women talk about seeing each other again but with all the boxes they are carrying they can't actually see each other's faces.
"50% off" means "50% off the usual price", ie, half price.
We use the reciprocal each other and one another when two or more people do the same thing. Traditionally, each other refers to two people and one another refers to more than two people, but this distinction is disappearing in modern English.
- Peter and Mary helped one another.
= Peter helped Mary and Mary helped Peter.
- We sent each other Christmas cards.
= We sent them a Christmas card and they sent us a Christmas card.
- They didn’t look at one another.
= He didn't look at her and she didn't look at him.
They helped to look after each other’s children.
We often stayed in one another’s houses.
NOTE: We do not use reciprocal pronouns as the subject of a clause.
(source: British Council LearnEnglish)