Start up cost is expensive. Kits, extra battery, atomizers, cartos if you use them, juice, passthrough, pcc, etc etc. Once you have everything and figure out maintenance cost per month for the occasional battery, atomizers or carts it isn't that much. I'm leveling off now and should be able to get my juice supply for $25 bucks a month, a little better if I look for sales, that is if I don't go juice crazy, add another $25 for supplies and I should be able to maintain at $50 a month or less. If I control myself and only get what I NEED and not everything I see.
If moneys really tight I could see someone getting by on about 1/2 that if they absolutely had to.