It is completely unjustified upgarde option just within months apart. Make up your mind what you want to do it with this site. I have no problem before paying high price because of quality stories. Secondly you taking months to post new episodes. So roughly in a year how many episodes we can read. 2 or 3. Also not to forget to read those you also have to spend money on it. I still don't have any problem but please again requesting you to make up your mind, sorry but have to say its feel greedy. I usually don't say anything to your money maters but looks like you put your step on your fans/readers neck.
Make things simpler. Put yearly prices once to enter on site and read all your updates without spending more. Even if its $100 or $200 a year. And please do not change further in just a month or two. After a year increase 5 or 10 percent.
Upto you, you are the boss.