Meaning
To be extremely, often unreasonably, expensive.
The phrase is a general exaggeration rather than a precise figure — it signals that the price felt shockingly high, not that an exact fortune changed hands.
Origin
Unlike many idioms on this list, this one has no single traceable coining event or literary source: it’s a straightforward hyperbole built on the everyday word “fortune” (a large sum of wealth), extended naturally to describe anything priced high enough to feel comparable. Its plainness is exactly why it has stayed so durable and universal — every era has its own idea of what a “fortune” looks like, so the phrase never goes out of date the way a reference to a specific sum of money would.
Examples
That designer bag cost a fortune, but she says it’s worth it.
Renovating the kitchen ended up costing a fortune.
Flights during the holidays cost a fortune this year.
A: “How much was the repair?” B: “Don’t ask — it cost a fortune.”
Frequently asked questions
What does 'Cost a fortune' mean?
To be extremely, often unreasonably, expensive.
The phrase is a general exaggeration rather than a precise figure — it signals that the price felt shockingly high, not that an exact fortune changed hands.