A carto has the coil and wiring embedded in the filler material. You can't get it out without breaking the wires. At 5 in a pack for $8, it's cheap to use them for a few days and toss them. Cigarettes were $4 and up for a pack a day. Cartos are around $1.80 for three days use. Why bother?
There are cleaning methods for rejuvenating cartos. Check out YouTube and also do a search on ECF for "cartomizer cleaning ".