Your apartment’s fee can be looked up very easily online, with soufun or some other site. I’ve never heard of it being different for different units, maybe if it is a mixed complex with some walkups and some elevator buildings?
I would expect to pay within 2-5 mao of one yuan per square meter per month and you are paying close to three. I might go as high as two yuan/metre for a very nice place or lower rent, but it does seem high.