Had a few extra hours earlier and decided to use Hopper's data to investigate a question I know many have asked before.

How much do you really save by flying Spirit?

Not surprisingly, it's not much. Averaged across all routes, flying Spirit was just $30 cheaper than the next best option. And that's BEFORE all the additional fees that they tack on. After we account for carry-on fees alone (under the most generous scenario), Spirit becomes the more expensive option on the majority of flights.