Gothic_Temptation 17k and Zongheng uses the same system in China. If and when they expand overseas, we shall see if they will try something new. It would be interesting to see different business models.
Why it's so expensive is because of demand and supply. It was optimized based on the D-S curve based on what patrons are willing to pay on Patreon (which is way more expensive).
They can still continue for another 2-3 years with the old contracts they signed with the publishers. It's still a question if the publishers will create their own sites and bypass WW and Volare, considering the recent government initiative. Volare signed with an author of a very old work who happens to own the copyrights to the translations. That can still work, but that will be in the minority.
For instance, China Literature (Webnovel's parent company) has 90% of all Chinese web authors under them. The remaining 10% are with the other publishers. Yes, you will be able to find a few authors, who you can sign directly with, but whether their works will be popular is another question.
I agree with you that the prices are high, and I suspect that there will be ways to make it cheaper in the future.