That was smart of them to take you up on your offer! It reminds me of something I read that said if you are trying to sell something to someone and they're budging, ask them what it would take to change their mind. It's kind of a trick question, because often, whatever they request can be provided (or at least an equivalent), and once the salesperson provides it to them, it's very hard for them to say no. Most people want to appear consistent in their behaviors.