Net, my running cost is $2/day vaping instead of what I spent smoking, and that's changing cartos every 4 days, not counting any reuse of cartos. Earlier I was running at $2.50/day, using a bit higher nic and the classic proprietary batteries (808, Riva, etc.). For me using a decent grade VV mod has been cheaper, as the little batteries did have breakage.
Here's my earlier $2.5/day:
Carto: $0.4/day (Catch an Eastmall coop and cartos end up costing only $0.8 each, the $0.4/day is based on paying more standard prices of about $8/5 pack)
Eliquid: $1.3/day (it's actually cheaper for me, since I DIY, but $1.2/day is a person vaping 3 ml/day of $12 eliquid)
Hardware: $0.8/day (At that rate you can buy a full new Riva Lite kit every 60 days, including shipping to cover the HW/cartos/eliquid.)
Now:
Carto: $0.5/day (I've recently gone to a different carto that's slightly more expensive)
Eliquid: $0.8/day (I've increased consumption to 6 - 7 ml/day, but my current DIY costs < $4/30ml, including all shipping and materials)
Hardware: $0.7/day (It could be less, but this just lets me build a kitty going forward, to buy the next toy. My $130 for a VV, 3 sets of batteries, charger is still going strong after > 8 months. I let myself get another mod, $160 with multiple sets of batteries, after months, just because I felt like it, not because my first one had any issues.)
So, I started at $2.50/day, I'm down to $2/day, it'll actually drop a bit more as I drop my nic more. The above are real, actual numbers. The 3 ml/day on 808 or 510 voltages represents a pretty healthy consumption level, I never was trying to stretch things out. The 6-7 ml now at higher voltages is likewise pretty healthy.
Did I spend more? Yes, for play stuff, things I use to pay it forward, some things that I just futzed around with, tried. I do, however, recognize that the hobby part is separate from the core vaping part. None of the things I use, or have used, are any secrets, I bought things from good vendors based on asking questions here on ECF.