I believe what you are talking about is implied odds vs pot odds. Implied odds is what you believe you can win if you hit your outs (say on the river) vs what you will need to bet. Assuming you hit your flush, do you believe the opps will call your bet (hopefully a big bet)? If so, the implied odds would demand you stay-in.

Also your particular situation, I would bet all the time, the person didnt bet very big (I would put them on a top-pair) and the second opp called (probably pair or drawing too). You also probably got pot odds too since if an Ace hits on the river, you might have the best hand. Im assuming the board didnt have an Ace so the opp betting might be betting the current top pair that flopped.