What do you feel is expensive? Most of them cost between $10-20..
Its not the price that concerns me but the "full 5v power" some have and others dont.
I just went thru this b4 I bought mine (I wanted 5v) so (FYI) the ones that have a inline battery are just 3.7v, but if you
buy a full 5v unit it wont run off a typical usb port so you will need to
buy a "powered" usb or a stand alone usb that has at least 1.5 amps (2amp is prefered).
Anyway, I got mine here when it was on sale ($3-4 less)
USB Passthru for GP VapoRite KR-808 w/ manual switch and it does kick some ....!! Like I said tho..you will need a wal-wart/car charger (2amp) to use it, otherwise you can get one that runs off your computers usb port but its only a 3.7v, and thats not going to kick (if thats what your looking for).