I'm not the expert. That being said, I'll try to break it down for you the best I can. I'm using american dollars, as I'm familiar with those.
I'll use simple Boge cartomizers as an example. I usually buy them 3 packs a time, for 20 bucks. There are 5 in a pack. So my total cost for a cartomizer is 1.33.
Other brands, and not being on sale will raise the price on these ... though I don't really see myself paying more than 8 bucks a pack for them at the present time.
What do I get for this. Well each cartomizer has a stainless tube, at the top is a cap, inside there is a coil, filler material, and an air tube, at the bottem is a 510 battery connection with a hole in it.
With the Boge cartomizer, I usually take the softcap off, and tilt the cartomizer enough to fill the filler, avoiding the airhole. I put in a few drops and turn it, and repeat the process slowly, until I put in 23-24 drops. It won't hold more than 24 in a 1.1ml cartomizer. I then let it sit for a minute or two before 1st vape. If you put juice in the airhole, it will come out the top or bottom, I usually just blow the excess out into a paper towel or so, if I'm a bit messy. I save the plastic condoms off of mine. I usually will replace the softcap with a driptip.
The amount of drops the cartomizer will take, depends on the size of the cartomizer.
Then you can put it on your battery and vape it. I tend to be a little paranoid about burning the filler, so I tend to refill mine long before they dry out, because if they do, the filler material will burn, and then I consider that cartomizer done, and needing replacement. I try to avoid this. They tend to last for me about 3 days of vaping this way, until the vapor production on them starts to drop off. The time on this varies a bit. I find the best way to get the most out of them is to keep them clean ... I use the plastic condoms, to store them when not in use. I don't tend to store mine for extended periods of time, I just think letting filler sit for weeks on end isn't appealing to vape.
They can be cleaned, by boiling them in water several times for about 5 minutes (boiling time) each cycle, replacing the water each time, then letting them dry, but I seldom go through that. When done the water will come out clean like you put it in. Don't boil the softcaps or covers, just remove them and replace them afterwords. Don't boil plastic cartomizers, they will just melt.
(Tanking a cartomizer ...)
Looks like this ...
You put a hole in the cartomizer above the bottem oring of the tank. You fill the cartomizer as above, and then you can fill the tank. The filler in the cartomizer wicks the juice from the tank, and you know when the tank is empty. I find you lose just a touch of flavor. The cartomizers however will last a bit longer like this. Perfect for on the go.
Now lets move on to atomizers.
Most atomizers cost between 5 and 10 bucks. There are some exceptions out there. I'm going to use a Joye 510 atomizer without a gold band, as an example. I can get 3 for about 25 bucks without trying very hard.
What do I get for that. Ok, I get a shorter stainless steel tube, inside that tube is a heating coil, a bit of wicking material, a ceramic pot, a bridge, and some metal mesh (what usually comes with an atomizer), and a 510 connection with a hole in the bottom it.
The both have the same function, vaporizing your juice.
At its simplest you put the atomizer on your battery. You prime it with juice (I use about 6-7 drops, the gold banded Joye 510's are supposed to be primed btw though I've never used them.), to get it wet. Pop on a driptip and vape. You have to keep the coil wet to vape, else it will dry burn and that will kill your atomizer faster than anything I have found.
When not in use, I tend to take my atomizer and rinse it out with hot water, blow out the excess liquid, and let it drain into a paper towel, battery end up, I give them 2 days off then. Eventually they might need major cleaning, but I tend to avoid this as much as possible. Most of the time this works very well.
When using atomizers I tend to rotate them, so I have a nice one ready to go.
I tend to use ice machine cleaner as a last resort, if water just doesn't cut it. I've worked in refrigeration a very long time, and its just been something I've usually had available. (There are many methods for this, some are better than others.) Of course you wash them out very well, and let them dry, before re-priming them. Most come back good as new, and the others, well they get thrown out. Some attempt to dry burn them in this process, to clean them up, and it works for many, though I personally have had very poor luck with that, and that is probably just me, so take that with a grain of salt.
I can tell you if you do use cartomizers that having an atomizer or two, for testing new juices is a good thing. Its a waste of a cartomizer and juice to fill one, and find you don't care for it. Whereas on the atomizer, that flavor will be gone shortly if desired.
I tend to use atomizers in bottom feeding devices which hold a bottle and a tube to the atomizer, which when pressed serves the function of dripping, but holds more juice in a convenient form.
If you have any questions, this forum is a great place to ask.
I have had atomizers last for 3 days, and others last for many months. They are supposed to be quite a bit more durable than cartomizers, and most of the time they are. I do know that you can get into bad luck with these at times though.
I believe that those who tend to take care of their gear the best they can, have better results than those who do not.
Personally I use them both, I hope the information is useful.
Happy Vaping