I used to think negotiations were simple - just come in with a reasonable, middle of the way set of terms, treat the counter-party as a reasonable, benevolent entity, and everything will work out all right. I quickly discovered that while there are some people who work this way, for the most part if you adopt this approach people will eat you alive. You won't even know what hit you.

I'd use the "reasonable terms" principle with friends I worked with for some time, or with people who have an immensely strong reputation for being reasonable (YC, etc.) But if you met someone two weeks ago, and they bring up the concept of an emotional bond into what ought to be a commodity transaction, alarms would go off in my head. (Note that it's easier to talk about an emotional bond when you're on the better end of the deal).

Mark probably is one of the very few people who work in a reasonable manner, but unfortunately for every person who works this way there are dozens of impostors who'll pretend they're reasonable and then eat you alive the moment you let your guard down.

So my advice would be the opposite. Unless you've worked with the person for a while, or have really strong evidence that they put insanely strong ethics before profits (and believe me, gut feeling is not strong evidence), or you've already indicated commitment, take the better deal.