These amounts and their increases are usually decided by the management company of the building. Often, the more amenities a building has, the more the maintenance charge is. Also the bigger the apartment the more shares a coop has and therefore they may have higher maintenance. One of the things you want to look into are the building's finances are. Is there a mortgage on the property? Is there an assesment for repairs? All this has to be taken into account.
Finally, some portion of one's maintenance is usually tax deductable. Find out from the Realtor you are working with. It's their job to get you this information.