I did morphine sulfate once, it took 40mg for there to be any noticeable effect with zero tolerance. I personally wouldn't pay this much, but I would say $10 per dose (30mg - 40mg).
It looks like you have a 120ml bottle at 100mg per 5ml. I'm coming up with $600 based on a 40mg dose at $10 a dose for the whole 120ml bottle. That seems a bit high.
Maybe I'm off on my math with the dosage... but I know it took 40mg for me to feel an effect off it.
I would also be careful who you give it to because at 100mg per 5ml, it seems like it would be awful easy to OD.
at 30ml, maybe $150 for the bottle?