In any case, so little nicotine goes into the juice compared to the amount of solvent that increasing the nicotine concentration even to very high levels had a negligible impact on the amount of solvent. And manufacturers aren't going to put less flavoring in.

I'm not sure of the chemistry in this specific case, but it sometimes happens that adding more solutes just causes a solution to get denser, so it doesn't decrease the mass of solvent per unit volume.