The restaurant offers very delicious food and it doesn’t even cost an arm and a leg.

This bungalow will cost us an arm and a leg; we should better start saving much more than we do.

Cost an arm and a leg means a lot of money or something extremely expensive.

The phrase doesn’t have any clear origin. It seems to have its roots in an expression from the nineteenth century ‘ … I’d give my right arm..’ which would show a person’s willingness to pay any amount for something he needs or wishes to have.
However, the phrase is associated with the world wars also where soldiers who lost their limbs were considered to have paid heavy prices, hence the phrase was born. Besides, obtaining an item during the wars was quite difficult due to shortage and rationing and therefore people would spend a lot of money on petty things too. Hence the saying ‘cost an arm and a leg.’