For $9.99 Kindle unlimited one can read as many books as you want with a limit of 10 out at a time.
Since WebNovel items are delivered by chapter, say at 8 SS a chapter on the cheap, a novel length production is around 4-500 SS, which equates to about $8-$9.99 depending on your cash for SS purchase.
While they offer a bunch of options, you are semi forced to seek out those options or be stuck with the release rate for your edition of choice.
Prior to going premium I spent most of my stones catching up on the stories that were important, and the subscription allowed me to casually pick up additions to my main focus.
Once the subscription went away though I just stick to those that really drive my interest because ultimately its is extremely difficult to justify spending $50-$100 a month much less $30 to get what collectively amounts to less than one solid novel of content. At least with the subscription, even after reading 10 chapters of filler, I can at least pretend that the potential content I have at my disposal is worth the price even if I never actually do stray from my focus group of works.