I am with you on this and after reading your post I wanted to see how much nic concentrate at 90mg nicotine it would take to make a liter of flavour, At 6mg which is what I currently vape, that is 67 ml of nic concentrate or just 2.26 ounces per liter made.
Roughly we can make 6 to 8 liters of nic juice flavour at my nic level. 24 to 30 liters for a gallon of 90mg. Get that down to 3mg and we have double the amount of flavour that can be made
I don't think I vape a liter a month, so a gallon should last more than two years!