in reality i dont know how much money you will actually save. your location says u live in china, im korean myself and in korea i know cigarettes are around 2 - 3 USD per pack, a good starter setup equipment is around 100USD or so, i spent around 140 ish becausei bought a silver bullet from altsmoke.com $100 and then i bought a MAP tank from cloudsofvapor.com $30. + tax on both.
you could buy around 60 packs of cigarettes with this equipment alone, then you need to buy e juices. i vape a lot more than i used to smoke, i probably go through around 3ml of juice perday, this is aroudn $2 worth of juice per day, if a pack of cigarettes is 3 dollars, then 300 cents / 20 is 15cents. so my vape cost is = to 13 cigarettes.
so if you are living in asia where cigarettes are rediculously cheap, and smoke less than 13 cigarettes perday assuming that you vape as much as i do which is not difficult because
vaping on a good PV with a good flavor of e juice is amazing, u will actually loose money.
if you smoke more than 13 cigarettes a day then u will slowly save money, if you smoke heavily like 2 packs a day or somthing, u will save 1.05 perday. so i guess around 4 months to make up the starting costs?
in the USA on the other hand cigarettes are double - triple the cost (california) at 6 dollars a pack, (30 cents per cigarette). so to match 2 dollars worth of 2 juice u need around 7 cigarettes. if you smoke 7 or less cigs perday before, you would loose money, say in the states your a pack a day smoker, you save 13x30= $3.90 perday. so it would take around a month and a week or so to make it pay for itself.
dont take this as fact. 3ml per day of
vaping is fairly heavy vaping (my opinion). and cigarette costs differ vastly, i heard in new york a pack is like $10, where in that case if u were a pack a day smoker u'd make up the cost within weeks.
i believe there are e-cig stores in china, if u live there u should go and try some out and see how u like it, if it gives u that relief satisfying feeling that a cig gives you, u might as well quit because eventually u wil get your money back as long as u dont go back to normal smoking, and its probably healthier for you to vape than to smoke, although i am not sure of this.
(NOTE: there maybe price disparity due to the fact that i have NO IDEA how much a quality e-cig costs in China, and how much e-juice costs in China. If these are significantly cheaper for equal satisfying quality, the cost of vaping may become significantly cheaper than the cost of smoking.)