Well, if you smoked a couple packs a day, at $5-$7 a pack, and an extra pack if you went out on the weekends, vaping gets dirt cheap in a hurry. I figure I was spending anywhere from $350-$450 dollars a month on cigarettes. It varied, because I varied what I was smoking. So my whole ProVari setup including batteries and charger, everything, cost me less than a single months cigarettes. After learning to wrap my own coils, and getting into rebuildables, my price per month went to just juice, and even when I was vaping nothing but Halo from a local store I'd have been hard pressed to hit more than $70-$80 a month for supplies. Between juice prices going down everywhere and dabbling in DIY liquid I spend considerably less now. Now a days, if I see something I want, I buy it. I am not a big name brand flasher, so most of my stuff, excepting the ProVari and batteries, are clones that I get dirt cheap by being willing to wait on fasttech. Even if you subtract out every single purchase I've made, I have saved THOUSANDS of dollars by vaping. That's not an exaggeration, that's just basic account balancing.
I do feel I saved considerably more than many people by buying a ProVari fairly early on though, rather than riding the upgrade train from station to station. I basically went from kr808d(cigalike, and the best one available at the time) to a couple Ego styles as soon as they came out, and shortly thereafter purchased a ProVari. Honestly, other than playing with mechanicals, it's only been recently that any devices that really compare to the ProVari have become available, and I'll probably upgrade my Provari to v3 when that rolls around instead of messing with any of them. Heck, if I decide to buy a new v3 mini I still won't be putting a dent in how much I saved.