Is it obligatory to fulfill a vow and pay the sum of money, after it was vowed to leave a job and find a new one, but then a promotion occurred in the current job, and the need for a new job ceased to exist?

If the condition upon which a vow is suspended is not met, then it is not obligatory to fulfill it, because a vow suspended on a condition is not binding unless the condition exists. Furthermore, you are not obligated to bring about this condition, by consensus. It is also mentioned that making vows is discouraged, and this discouragement indicates disapproval (makrooh), not prohibition (haram).