If these were anonymous strangers, I think the best move Mike could make is to give everyone EXCEPT Sam the $1200, and keep $2400 for himself.  Of the remaining four, Sam was the least trusted, so when he said he was shorted, but everyone else got what they expected, they might still just vote to accept it anyway.  Unfortunately these were YouTubers, people with public images to maintain and who may very well know each other more personally; so some fair play was to be expected.