It quite does matter what the concentration is, dose makes the poison, and the half life of nicotine is so short, dose over time makes the poison.
The Nicotine's LD50 is .5-1mg/kg, as in 25mg-50mg for someone at 120lbs, 50mg-100mg for someone at 240lbs.
It's half life in the human body is 1hr.
The really bad stuff, ~270mg/ml would be diluted down to ~46.5mg/ml in 18mg/ml recipe. Maybe around 65mg/ml for 24mg? Which again, is consumed over time. What's in your system is cut by half every hour.
The worst nicotine poisoning I'm aware was a case where
40% nicotine was added to beef in 2003 with a net result in tests at 300 mg/kg. Out of the 100 people who injected the beef, only 2 were admitted to the ER. One for atrial fibrillation, one for nausea, vomiting, and complaint of rectal bleeding. One hospitalization, a pregnant woman with episodic vomiting.
I don't mean to dismiss the BE case as being trivial, it's not. Fortunately at the concentrations offered the net result is a toxic, not lethal. Those at the highest risk are the folks working with it who would need to take extra precautions to deal with this level.