The idea that flight search tools "fuel" budget planning is a bit strong; history shows us that preparing a trip has never been limited to just the transportation cost.
The playbook has always told us that a cheap airline ticket does not guarantee an economical trip if the cost of living on site is exorbitant.
For example, a good price flight to Tokyo means nothing if a daily meal costs an arm and a leg, and we've seen this many times.
These tools can help, but they do not change the fundamental need to consider all local expenses.