For the subject question: "Do you like to see other men cum?" , my answer would be "Sometimes. Depends."
For original questions:
"I think it's interesting that even in straight porn, the cumshot in the end is considered "the money shot". Why is that?"
The effect part of cause in effect. The woman has the hot bod. The act is stimulating. The money shot represents the result of those things, the "payoff" of the hot chick and the sex act. Since it's a "payoff", hence "money shot"
"If are straight, I know you are not interested in watching other male performers, but what is it about them cumming that is so appealing in the scene? Is this when you usually cum? "
It's appealing because it's that final out to seal the game, the final kill in the movie so to speak.
Not necessarily when i cum, although the time the sex act(s) take in the video/movie may coincide with the amount of time it takes from the start of masturbating to ejaculation. Sometimes multiple scenes are required, and how likely it is to be in sync is the question. Sometimes there may be a specific portion, like the unhooking of the bra and breast revelation that will send me over the top if i watch it over enough times or have been jacking long enough.