Even the cheapest first class flights will result in sticker shock—if you're eyeing a seat upgrade on a US flight, premium cabins usually cost around three times more than economy class.

That's because for most fliers, business or first class is often prohibitively expensive and a rarity saved for special occasions or occasional upgrades. However, Scott's Cheap Flights ...

The cheapest one-way ticket found by ... flight was $980 in economy or more than $2,500 in first class. Still, the new nonstop flights the airlines have added appear to be cheaper than flying ...