Arbitrary example: GRR -> Copenhagen roundtrip is ~$1,100 USD. From NYC or SF I can do that for ~$400-$500. Pretty much anywhere else I could pick has a similar differential.

That's a massive cost difference, especially when you're looking at 2-4 person vacations. That's a problem in pretty much every rural area (flying out of Ithaca was expensive as heck). I'm able to travel way more as a result.