36x 0.5 cents is 18 dollars. So they started spending on security and it made them unprofitable perhaps. Retail runs on razor thin margins, so there may be some substance to this 36x number.
It's not a 'trope'. It's a fact. Major retailers, including Walgreens have net profit margins in single-digit percentage points (it was 4.1% this quarter). The reason they make large profits is that they do large amounts of business (their revenues were 28 billion this quarter).