[Sombre]

I think CBM is worthwhile even if you only play SP, because it evens out the difference between things which are hugely cost effective and those which are, essentially, far too little bang for you buck.

You might really like the concept and look of a certain summon, for instance abysian smoulderghosts. But whenever you use them, they do worse than far cheaper regular troops, which is discouraging, so you stop using them and almost inevitably drift towards stuff which works well, rather than stuff which is interesting (partly because the stuff which works actually survives and is affordable, while the other stuff dies horribly). Now if you introduce CBM, it makes those smoulderghosts, if used in an intelligent way, worth the cost. That idea you had of using them with sulphur clouds becomes feasible, because you can actually afford more of them. So you're able to make use of the units and tactics you want to without them being overshadowed too horribly by obvious better choices. They may still not be optimal, but at least they work ok.