Hi everyone I just picked upa new njoy npro starter kit last night. Kind of an inpulse buy but a good one I think. Haven't really used it much as I wanna finish my standard cigs before I go with the njoy completely. Just have a few questions I've read where the njoy cartidges are expensive compared to other brands. Is there a cheaper way to use the njoy npro other refills? How does the liquid refill work and where is a good place to buy here in the US