Lol Ludwig...... This scenario, to me, is an example of Capitalism at work.
Emotions aside, you don't know me and I don't know you.
In effect, we actually both have nothing...but the power lies with the person who has the £100 to begin with. They are in a stronger bargaining position. It would rarely happen that the person with £100 would keep say £30 and part with £70? Actually they still make £30 quid out of it?
Say I have the £100, it is in my interest to keep as much of that as possible.
Jake mentioned 20%, so say after intense debating for about an hour, I put it to you that whether I leave with 80 quid or not makes no difference to me whatsoever but that you lose 20 quid, 20 quid which you don't have presently, then are you telling me that the majority of people would not as a final offer accept the £20 quid?
The bargaining power and ultimate gain is with the person who starts off with the £100?