you can get a good setup for ~$50 then the heaviest users will spend like $30/month on juice (most users will spend a fraction of that)
If you mix your own juice you're approaching savings that are better on an order of magnitude.
once i found some diy recipes that i enjoyed, i made a pair of 120ml, and the cost savings from those two bottles alone covered all the ingredients and equipment (beakers, stirring rods, scale, bottles, etc). diy is especially worthwhile if your device guzzles juice like my geekvape griffin tank does.
diy or die on youtube is a great resource, here's one of the recipes i make regularly: https://www.youtube.com/watch?v=QlI8CvT8SCA
If you're buying domestic juice you pay a premium for nothing special, from what I can tell. Also, the chances of it being made in a proper factory are basically nil. It's often someone else's DIY garage juice at a 10000% markup.
I haven't kept up with the new FDA guidelines since starting DIY about a year ago, but from what I remember a lot of the little garage brands are going to be in trouble. My buddy used to work at Apollo out in Concord and I know they take their juice seriously. I think it's shitty, but it's not because the line is dirty haha. Molecule Labs out in Benicia has a pretty cool facility as well.
Three 120ml bottles last me close to an entire month. Local stores around here are also a rip-off (near Austin, Texas).
Vaping is something I do A LOT of while post-processing photos! Do you perhaps have a photographic interest?
That's more than 10ml a day! I know you're going to disagree and try to convince me otherwise, but that is an INSANE amount of liquid.
I should try and cut back some and reduce my nicotine dosage of 1.5mg down to 0mg but I don't mind the nicotine.
I'm also addicted to coffee so about 2-3 full Yeti cups a day. Woe is me!
Sigelei 50W Watt Box Mod Kanger-subtank with OCC Vertical coil. 0.5 ohm
liquids: Ultimate Kringle (every day juice) Castle Long (every now and then)
As others have replied and as might know, the world of ecigs is rather large, poorly detailed (mostly), and can be expensive to start. That equipment worked really well for me at the time. But the "go to" gear may be different by now - I would stress that you research before you buy.
I have learned everything i know about ecigs from friends, ecigforums, youtube rewviews, and buying a lot of crappy equipment.
best of luck.