That's a slippery slope....
If all you ever bought was one single RBA, kanthal, cotton, and e-liquid, then sure, you'd absolutely save money. Kanthal and cotton is cheap, and once you get a good build in it, a single coil could last for months with proper care.
Here's the problem: You won't buy just one. You'll buy one, love it, then immediately wonder what other style tanks or drippers are like. And you'll need to buy one of those too. And don't forget the new mod you're going to need to run that new dual coil tank. And the other mod you'll need to run that other tank.
It's a vicious cycle, to which I haven't found the end yet.

I kind of like it though. My wife? Not so much.