Well they all have to make a profit, so they will set thier own price they can do business at, and keep your names safe. Some people, myself included would pay extra to keep any high-value names safe for the long term. But then of course there are others that simply rather price them high (20-30 dollars a name) without any extra security. That can get expensive when you have many names to renew.
Again, that is up to the owners, but sometimes you can make offers. That does not mean low balling them with a 10 dollar offer on a 100K name. Make it resonable. But research the name first. I had a guy that bought a name he thought was a perfect name for a parenting site, but turned out to be a term used for adult content too. He had paid over 2000 for the name.