Audio problem: When Jack digs for the statue in the puddle, and he hits it, it makes a sound like iron against ceramics, but the bunny statue is wrapped in hay and cloth. The wrapping is so thick that the spade would not be able to touch the statue, so it would make no sound at all when he hit it with the spade.
Audio problem: When the military asks Jack where the heart is, after he replies it's in a safe place, another guard uses his rifle to hit him in the groin - the hit is clearly fake.
Answer: Any emerald over 1 carat in that beautiful cut and condition would probably go for over 250 million. Real emeralds over 5 carats are rare and the price goes up exponentially after 2 or 3 carats. 305,000 per carat after 5. So yeah that one was probably like 800 or more carats.