​​Which is most Expensive liquid in world?

Scorpion Venom is the most expensive liquid on earth at approx $39,000,000 per gallon.

Scorpion

Scorpions use their venom as a defense against predators to paralyze and kill their prey.
The venom is comprised of groups of complex molecules called neurotoxins. These are proteins consisting of 60-70 cross linked amino acids that when injected attack the nerve cells of the victim causing paralysis and death. 
Research suggests that scorpion venom can block bone loss, making it a useful substance for treating conditions like rheumatoid arthritis and osteoarthritis. The protein found in the scorpion venom, however can be used to treat pain in humans who suffer from multiple sclerosis, inflammatory bowel disease and to make anti-venoms.