Comment by array_key_first

The lower COL areas are lower because they're less economically viable, and therefore less desirable. The job opportunities and income will, more or less, match the lower COL.

Theres some exceptions, like rural doctors can make more more than city doctors due to high demand. But the less "physical" your job is, the rarer these exceptions become.

For software devs, you can move out of silicon valley. Maybe to Texas. And now those 1.5 million dollar homes are only 700,000 dollars. But your salary will reflect that.