It actually makes more sense than it might seem upon first glance, at least in the context of people moving from Texas.

Texas' minimum wage is the federal rate of $7.25/hr. Washington's is $17.30/hr, while Seattle specifically has it even higher at $21.30/hr

Cost of living in Seattle is around 55% higher than in, say, Houston Texas, but its minimum wage is about three times the amount.

Add on to that the fact that Seattle has an expansive public transit network that costs much less than owning a car (about $108/mo for unlimited public transit rides on all buses, sometimes paid for entirely or in part by your employer), and there are definitely ways people can drive their cost of living down more if they want to.