I have been seeing around this site that some refill their own cartridges. Is this really cheaper? What liquid do you buy? And can anyone that does this, tell me how they do it? I found a video where you just take a paperclip and pull out the innard where the smoke comes through, and drip your liquid in there. I am very interested, as the whole reason for going electronic was to save money, (not the whole, but a big one!) and am interested to hear everyone's experiences.