An arm and a leg

Meaning: 
describes anything that is considered to be extremely expensive or extremely pricey
Synonyms:
a lot of money, a pile, big money, a packet...
Examples:

1. These shoes cost me an arm and a leg.
2. The trip's cost an arm and a leg but it's well worth it
3. He'd only just bought it when we met. It has cost him an arm and a leg