WAY TOO MUCH! Lol! Once it became a "hobby" and not a "habit" I seem to spend a lot more - especially after I realized the huge difference between clones and authentics. I don't mind spending the money, though. It has kept me away from cigarettes for more than 3 years and I'm not even buying juice with nicotine any more. That, alone, is worth just about ANY amount of money.
If I'm not buying any devices on a given month, I probably spend less than $50. I mostly vape juices from ITCVapes.com and Dr. Crimmey's and their juice is as affordable as any I've found and their flavors are (to me) comparable to MANY of the high-end retailers; and, in many cases, I actually prefer their juice to the high-end stuff I've tried.
This month, though, I've bought 1 new RDA (Hobo V2.1), 2 new tanks (Aspire Atlantis - one was for my wife), stocked up on juices (about 1000ml) and just ordered a Hana DNA 40 (in Olive Green). So, my bill for the month was more like $550. OUCH! On the bright side, there's only 2 more RDA's (Veritas & Vertex) on my wish list, currently, and my wife is happy with her Lemo and here Atlantis; so my VapeBill should be a little smaller for a while. Lol!