4 ml per day.
Now I'll try to calculate my spendings.
For liquid: $0.03 per ml. $3.60 per month. And I slightly exaggerated my costs on liquid...
Other recurring costs:
2 premade coils from FT - $0.11 per month
Cotton
Its tough. Lets say it is $0.10 per month
Total for my vaping recurring costs: $3.80 per months.
I have bought nothing in 5 months. I have used only Vamo ($30) and atti ($9) which came with 2 protank coils (rebuildable). They will last more than 5 months, but lets just suppose I need a new vamo every 5 months. So, price for hardware is 39/5 = $7.80 per months.
So, my total monthly spending on vaping is less than $11.60 per month.
But of course I spent some money on things I do not need Aerotank, RBA, RDA
Some other stuff and flavorings.