Printer ink is assumed to be the most expensive liquid on Earth. If you believe the many websites that quoted the figure above. But little research learns that this is figure is -- of course -- incomplete. Another graph (source: CBC) shows that the most expensive liquid is not printer-ink but perfume:
One can imagine that -- like nasal spray -- the medical world must be able to produce liquids that are of even greater value than printer ink or perfume because of their life-saving capacities. And how much would a farmer in dry lands estimate for that little bit of rain saving his crops and family?
Apart from knowing what liquid-spilling should be avoided, graphs like these are not very useful. They make clear though that we should not leave it up to mother nature; most lucrative liquids are man-made (including blood).