Hmm. :/ Quite a bit: nearly $650 (in US dollars -- around €470) in 46 days. BUT, a) that's for two of us, b) everything is much more expensive where we are, c) this includes over a dozen flavours for DIY, d) this includes every single thing, down to bottles for DIY, wick material, every tiny item, and e) we've still spent less (slightly!) than we would have on cigarettes!!! I keep a log of everything spent, and don't let us get above what we were spending for the nasties.
We just have 5 eGo batteries (only one of which is a VV), 4 Protank Minis (plus two nearly useless fake ones), 5 C5 atomizers, extra coil heads, over 20 10-ml bottles of ready-bought
e-liquid, 15 DIY flavours, pg, vg and nic liquid, bottles for making
e-liquid, wick, wire. So, yeah, we're just small-time, with no fancy equipment or mods (but a whole lot of juice!).
I have to admit, though, if it were only my husband, it would have been a lot less -- two batteries, two c5 atomizers, two,
maaaaaybe three e-liquids.

So, yeah, I'm the one who drives the spending with all my different flavours and nicer tanks, but hey, still less than than ciggies, and we're having fun, so wooo!