The secret to breaking even is finding a mod that you like, juices you love, and some repeatable form of atomization. Once you do that you stop ordering everything in a search to find the one you like. It's expensive until it becomes mundanely satisfying.
I spend about $35 a month on 150ml of assorted Dekang juices in the 50ml size and I run through 2 or 3 boxes of cartos a month at $7 each. I think that will be reduced after I bought a Vivi Nova this month. All I'll need is wick/coil assemblies ($3 each). One of those lasts a week or two and is really easy to change.
I was a pack a day smoker almost 3 years ago. Even now, a carton of Pall Mall ultra lights costs under $40 in Georgia.
You should order some extra head from the stardust which have the better silicon tip and you have say 4 tanks in rotation different juices, if a coil blows you change the head and in your own time rebuild the coil itself in the blown head when the one you're running blows switch again, I calculated my repair cost to be around .20 cents per month in wire and wick, and the roll you buy could easily outlast your vivi before you crack it with juice or a drop.