- Both expressions mean that something is very expensive.
- Cost a bomb is more common in British/Commonwealth English.
- Cost a pretty penny is used more widely but can sound slightly dated to some.
Explanation
Origin
- Cost a bomb: British English, likely emerging after World War II. It's hyperbole, comparing the high cost to the immense expense or destructive impact of a bomb.
- Cost a pretty penny: Older idiom, dating back to the 18th or 19th century. Pretty in older usage could mean 'considerable' or 'substantial' (as in a pretty sum). A penny, though a small unit, could represent significant value historically, so a 'pretty' one meant a lot of money.
Synonyms & Related Expressions
Alternatives
Slang/Informal:
- Cost a packet (UK slang)
- Cost the earth (UK/Aus slang)
- Cost a grip (US)
- Big bucks / Serious coin
Vulgar/Emphatic:
- Cost a fucking fortune
- Expensive as hell / Expensive as fuck
Milder/Formal:
- Represent a significant investment
- Command a high price
- Be of considerable expense
Situational Appropriateness
- Cost a bomb: Informal. Primarily UK/Commonwealth English. Avoid in formal settings.
- Cost a pretty penny: Informal to semi-formal. Widely understood but can sound a little quaint or old-fashioned. Generally acceptable in most everyday conversation.
Misunderstanding Warnings
- Both are idiomatic. Bomb doesn't relate to explosives directly, and pretty penny doesn't mean the coin is attractive. Both simply mean very expensive.
Examples
Cost a bomb:
- That renovation must have cost a bomb! (UK/Aus)
- Getting tickets to the final cost a bomb. (UK/Aus)
Cost a pretty penny:
- Her diamond necklace cost a pretty penny.
- Maintaining a vintage car costs a pretty penny.
Dialogue
Social Media Examples
Response Patterns
- (Same as for Cost an arm and a leg) Agreement/Empathy (Tell me about it!), Inquiry (Really? How much?), Sharing similar experience.
Common Follow-up Questions/Actions
- (Same as for Cost an arm and a leg) Asking for price, discussing value, justifying expense.
Conversation Starter
- No. Comments about the price of something specific.
Intonation
- Similar to cost an arm and a leg. Said with emphasis or a low whistle to indicate high price.
- Cost a bomb: Stress on COST and BOMB.
- Cost a pretty penny: Stress on COST, PRET-ty, and PEN-ny.
Generation Differences
- Cost a bomb: Common in UK/Commonwealth across generations, maybe slightly more Gen X/Boomer but still used.
- Cost a pretty penny: Understood by all, perhaps used more often by older generations (Boomers, Gen X). Younger speakers might favor cost an arm and a leg or just really expensive.
Regional Variations
- Cost a bomb: Predominantly UK, Australia, New Zealand, Ireland. Less common in North America.
- Cost a pretty penny: Used across English-speaking regions, perhaps slightly more common in US/Canada than 'cost a bomb'.
Cost a bomb:
Cost a pretty penny: