This question is locked. I wanted to post an answer saying that the past rent really doesn't matter. The poster has three options: accept the increase, find a new apartment, or negotiate the rent (with find a new apartment the backup). This is not in the range of answers on the question so far, and I think it is a useful view. I don't know what the torrent of answers has been to cause the lock-it has been 21 hours and I know people are sensitive to rent increases. How do we allow on-topic answers (if you think mine is) and stop the (presumed) stream of bad ones?
The linked question had a series of comments that resulted in a total of 8 moderator flags. I deleted the comments and to stop new ones, put a temporary lock (1 day) which I've just removed, if you wish to offer an answer.