Here’s a stab: If I understand you correctly, then every observer’s experience is indistinguishable from every other’s, so my credence in the proposition “I’m in room A” is 0.999 and my decision policy is “Bet that I’m in room A.” If 100 trillion + 100 billion people choose room B, then 100 trillion will lose and 100 billion will win. If 100 trillion + 100 billion people choose room A, then 100 billion will lose and 100 trillion will win.
Here’s a stab: If I understand you correctly, then every observer’s experience is indistinguishable from every other’s, so my credence in the proposition “I’m in room A” is 0.999 and my decision policy is “Bet that I’m in room A.” If 100 trillion + 100 billion people choose room B, then 100 trillion will lose and 100 billion will win. If 100 trillion + 100 billion people choose room A, then 100 billion will lose and 100 trillion will win.