Yeah, it sucks but it's still the best way for the vast majority of creators to earn money. At least the author of a premium series gets an editor and Tapas then basically becomes their publisher. For everyone else, Tapas is just a site on which they can upload their comics. They can make money with adds and tipping but Tapas still keeps 30% of the add-revenue (again, they do nothing other than providing a platform and still keep 30% of it). The tips go directly to the author but even the most popular series aren't tipped well. Most people tip significantly less than $1 ( the amount of people who only tip 25-50 ink, which is about 3-6 cents is quite shocking) and there aren't enough supporters.
So yes, it sucks that Tapas keeps 50% but out of all the shitty options there are, going premium seems to be the least worst.

I signed up to Tapas for this manga. Does anyone know the percentage that the author gets from this website?