I started with a $90 "starter kit" from
http://store.smokingstick.com/, and it worked great - it included a spare battery and enough nicotine cartridges to last me about 6 weeks. It was great until I lost it, at least. I ordered a replacement battery and some spare parts, but their shipping is so slow that I ended up getting a $60 unit from Amazon - which showed up three days later but didn't work (only one of the two batteries worked) so well. After I used up the cartridges that came with it, I found a brand called "Pure" in a headshop and spent another $40, and (shocker) it didn't work at all, not once, not a little bit, not at all.
In the meantime, I'd convinced a few people to switch to electric, and they all got 510s from
Cignot your Midwest Electronic Cigarette store., who also sell e-liquid. Even though my new smoking stick worked fine, rather than get caught up with "subscribing" to get nicotine cartridges for $40/month, I switched over to cignot and started buying e-liquid in larger quantities - and at lower nicotine levels. A week or two after getting the 510 starter kit for $60, I went ahead and got three spare batteries / atomizers, a pair of 510 mega batteries and a mega PCC.
Now, four months later, my 510 batteries are starting to die out, so I'm moving to a larger battery (eGo) and instead of continuing to mess around with refilling my own cartridges, I'm trying out the "tank" system - thankfully, I CAN use my supply of cartridges with the new setup since the new battery is also compatible with the 510 atomizers - I've got a stockpile of empty cartridges and 510 atomizers. I've tried the "cartomizers" out as well, and they work brilliantly, but they only last for a few days - they're perfect for emergencies or a night out, but the fact that they basically die after just a few days (invariably just after I've gone to the effort of refilling them) is a little dispiriting.
All told, I've probably spent about $700 total on the e-cig thing, but I haven't smoked a real cigarette in over 9 months, and I've got a stockpile of spare parts laying around - and a pair of eGo-T's in the mail!