Well, 8 or 9 bucks for 5 cartos is not much more than buying the empty ones. But if you refill them, you can re-use them for several days, maybe even a couple of weeks.
juice is around 50 cents a ml, so that would be $1.50 for 3 cartos a day versus the $5.00 a day for 3 prefilled cartos.
Granted, that's still cheaper than smoking 2 pad cigs.
So the difference money wise, is about $150 a month for prefilled and about $60 for filling yourself.
The advantage of using prefilled, is that you get a new cartomizer each time, and you don't have the (small) hassle of actually refilling them. Just pop one on and go.
The advantage of refilling is that you have a vast, almost limitless variety of flavors to choose. And, of course, it's cheaper.
If those are prefilled cartos at Myfreedomsmoke, I wouldn't order a huge supply until you or your Mom has tried them. Prefilled cartos are not known for having the best tasting
juice.