My guess is that the next goblin attack will come before an opportunity to leave peacefully or renegotiate. Of course, the adventurers might fight their way past the goblins and leave the villagers to their fates, but any such possibility will probably be ignored.
Now, my advice to you is that, when you find yourself in such a situation, defeat the goblins but then tell the villagers that you are going to report them to the guild so that they cannot get any further service, unless they sign a document indebting themselves to pay twelve times the originally promised sum (twice the fee per goblin) plus 3% interest per annum, compounded, and cane the chief as you watch.