If you live on the east coast you can get a discount flight to London for only $200 round trip. When these sales come up a group of my friends grabs tickets and go together, it's become a tradition.

San Francisco to London can easily run $2000 coach. That said, you're absolutely right! It's always possible to find a way to get around for much less than typical full price, and you are very correct to note this.

However, is it perhaps possible that the precise numbers might not be particularly relevant to the point? It's still at least an order of magnitude more than the cheap flight, for two major destination cities about as far apart and Detroit and Dallas.

Trying randomly for Detroit to Dallas vs Detroit to London on Oct 1 it was £51 vs £133 single. The London routing involved changing in Reykjavik though.

For anyone curious how that ~$170 USD fare is possible, it's WOW airlines and doesn't even include an overhead bin. It's great that WOW exists as an option, but it's hardly standard.

For example, from St. Louis, the cheapest round trip is in the ~$900 USD range.

The lack of overhead bins makes me go WOW.