would give your right arm for something/to do something

give (one's) right arm

A figurative phrase that highlights one's interest in having something or eagerness to do something. A: "I'm going to the concert on Saturday!" B: "Aw man, I would give my right arm to have tickets to that!" I would give my right arm for your sister's gorgeous hair!
See also: arm, give, right
Farlex Dictionary of Idioms.

would ˌgive your right ˈarm for something/to do something

(informal) want something very much: I’d give my right arm to own a horse like that.
See also: arm, give, right, something
Farlex Partner Idioms Dictionary
See also:
  • a bird in hand
  • a bird in the hand
  • a/the feel of (something)
  • (I) wouldn't (do something) if I were you
  • a fast talker
  • a straw will show which way the wind blows
  • a spoonful of sugar helps the medicine go down
  • a crack at (someone or something)
  • all right
  • (you) wanna make something of it?