If you go fishing for an afternoon or a night on a water where carp are accustomed to bait, the difference between a cheap and an expensive ball is small enough not to lose sleep over it. The same applies if you mainly need volume. Anyone wanting to lay a bed on a large lake needs kilos, and there is no shame in buying those kilos cheaply and choosing your hookbait separately.
In cold water, a carp eats less and more slowly, and then the question of how long you keep releasing bait suddenly becomes the most important one there is. A ball that does nothing after an hour is lying there for nothing. The same applies to waters with high fishing pressure, where the fish know the bait and notice the difference between a real attraction and a mere aroma. And it applies to any baiting campaign that runs for longer than a week, because you are building something up and you want the fish to encounter the same thing every time.
The shortest version: cheap bait is fine if you are fishing for fish that are already willing to eat. As soon as you have to persuade the fish, you want a ball that has something to say.
How do you build volume without feeding a hundred kilos of expensive bait?
By separating the bulk layer from the quality layer. You add volume with what is affordable, and you ensure that what lies in between and what hangs from your hair is the most interesting thing there.
On small bodies of water, this is hardly an issue. It only becomes a real problem on large bodies of water, where you can't achieve anything with just a handful. Mark de Zwart, who fished the French lakes near Bordeaux, explains why: