A few years ago I could buy litres of the vaping base and nicotine.
EU came in and said we must protect the children and forced that nicotine bases must have maximum concentration of 20mg/ml and can’t be sold in a bigger volume then 10ml. The safety caps are cool, the forced maximum concentration and artificial max is not because it creates shitton of instant plastic vape.

Now, if you want to save both time and money by making a bigger “tank” of it, you will find out sellers basically giving you ~30 of these 10ml nicotine bottles in a pack (called boosters).
You empty them yourself into a big one (with some amount of raw base to dilute for given concentration) and now there is 30 plastic bottles ready for trash, yay.

Note: I stand behind vaping as just a bit safer, less smelly way for nicotine use.
If you smoke, try vaping, otherwise don’t, you don’t need it.
One-time use vapes should have been banned a year ago, that shit is pumped with nicotine and the amount of waste is crazy.