If we're talking lower end budget here, that is below $40 just for an e-cig top. The Carto tank has these advantages:
-to my knowledge the best tasting leak-free solution with a high capacity
-seems to last longer than a clearo atomizer head
-easy to spot quality manufacturers (unlike a lot of clearo heads)
-readily available anywhere
-hassle free apart from punching holes, but there's tools for that
cheap RBAs in a nutshell:
-lower maintenance cost
-fun to play around with (you can try literally anything for wick-n-coil setups, get creative)
-taste as good as you make them, it does get very good
-not always easy to get started with, might require light modding
-not always leak-free (a genesis will always leak if you turn it upside down)
To be quite honest I would've skipped past clearos to a carto-tank if I knew what I know today.