The practical framework
The first mistake is comparing averages instead of your life. The second is comparing monthly costs while ignoring the first-year cash hit. The third is treating salary, taxes, benefits, and housing as separate issues when they all hit the same checking account.
Another mistake is assuming the cheaper city will support the same lifestyle. If the new location requires more driving, paid activities, flights, or childcare, the savings may be smaller than expected.
Finally, do not ignore exit cost. If the move fails, how expensive is it to reverse? A decision with low monthly savings and high exit cost deserves extra caution.
What to do next
Run your numbers through the tools, then replace assumptions with quotes. The goal is not to predict every dollar perfectly; it is to find the expensive surprises before they become commitments.