I have 2 DIY vapes that I switch between all day long, they both cost me about $.09 per ml ($2.70 for a 30 ml bottle), 34 mg peppermint and 34 mg cinnamon red hots, plain :)
My wife is easier than that, she vapes a no flavor 18 mg 75vg/25pg juice. Hers cost me less than $.06 per ml (<$2.00 for...