This belief is problematic because real (a.k.a. non-bullshit) jobs are typically priced based on the value of what's delivered, not the residence of the person delivering the value. Like race and sexuality, residence is wholly unrelated to the job.
I'd consider your predicament to be unfair. It's also not fair that garbage men work 10x harder than you for a fraction of your pay. Oh well.
Whether it is fair or not, this is definitely not true. Companies tend to pay what they can get away with, which means paying less in lower-cost-of-living areas. The people who assemble iPhones provide tremendous amounts of value. But they make around $4/hour. If you bumped that to $8/hour, Apple would still be tremendously profitable, but they assemble their phones in cheap labor markets where they can get away with paying less. Meanwhile, companies hiring in San Franscisco generally pay skilled workers higher than companies hiring in Oklahoma (let alone overseas), because no one would agree to work in San Fransisco on an Oklahoma salary.