What offended Pentangeli wasn't the fact that it was a C-Note. He was willing to negotiate with the Rosatos out of respect for Michael,but that doesn't mean he liked it.
His position was one of gracious compromise. By swallowing his pride for Michael,his only face-saving move was to perpetuate the illusion that he could have taken the Rosatos,but chose not to in the interests of peace.
Then Rosato blows it by reducing it to something as venal as money. It's just like when Bonasera asks Vito "How much shall I pay you"?
In both cases,the greater sin was assuming that a "man of respect" would freely offer the respect of his friendship to anyone with some money.
Bingo. I do believe you've nailed it. Funny how I didn't see that until now.
In light of what was about to happen then (the attempted strangulation of Pentangeli), apparently Carmine Rosato couldn't resist the temptation to stick it right in Frankie's face...as a last gesture of insult just prior to murdering him.
Very "classy"...
~ Q
