The stock coil versus rebuildable dilemma rears it's ugly head for most of us vapers sooner or later. Unless you are filthy rich, eventually, buying those stock coils starts to feel like your money is going down the drain.
Always worth remembering though, it's still a helluva lot cheaper than smoking cigs and the health benefits are immeasurable, as you no doubt know.
If money really is an issue though, as it was for me and many others on this forum, eventually, you will want to explore the world of rebuildables. It really isn't dangerous, it will save you a fortune and you may not realize yet but, the vaping is often a lot lot nicer with rebuildables.
To start with you will need to spend a little money though to buy a few basic tools like some scissors, some wire cutters, some cotton and some pre-built coils but you soon get that back with the money you save.
You tube is your friend and will teach you all you need to know.
Below is a typical review of an RTA including a demonstration of how to rebuild the device.