It's pretty standard that they try to put that in the contract and even try to enforce it. After my first year lease was up at the place I'm currently at I told the owner I'm not paying 10% more and in fact was not willing to pay even the same price as rental rates had dropped all around the area. I told him we needed to get our rent reduced or we would move. At first he said he'll keep it the same and I told him that wasn't good enough. The next day he agreed to reduce it.
Then we renewed again this past June and he wanted to raise it 10% again and I told him I wasn't willing to pay the increase. Didn't go for a reduction, but ended up agreeing to keep it the same. I think it's pretty easy if you pay your rent and don't cause problems. They know it will be hard to find another tenant that always pays the rent on time and doesn't break things.
I don't think everyone will always be able to get a decrease like that but you might give it a shot some times, especially when rates in the area are going down and you can move to an equitable place that is cheaper. In your case that is very good that you got to stay at the same price. Good on your part for being firm and being willing to move if push came to shove.
Rates seem to be going up now so next year, if we stay, I might give in to an increase to get it back to where it was in the beginning.
