It has been found that 94% of Euro notes in Spain contain traces of Cocaine. The Average Euro note contains 25.18 micrograms. If this is true one could collect the particles and turn a fast buck. But how many notes would you need to collect a gram of 'Charly'.
1g / 25.18µg = 39,683
6% of notes would not carry any so total notes needed would be 42,215
The lowest denomiation of Euro tested is the 10- Euro note so you would need to borrow 422,220- Euros from the bank in 'Used' notes to obatain a gram of Cocaine. Which has a street value of 350- Euros.
If the Spaniards were not sniffing so hard it might become more attractive but at the moment I would stick to your regular dealer.